A TYPE
See JACK.

A-D CONVERTER
Short for Analogue / Analog to Digital Converter. Changes a continuously varying electrical signal into a stream of binary data. Found in computer soundcards, MiniDisc & CD Recorders etc..

A.J. / AJ
n. Jargon for an Adjustable Spanner. (UK) Known in the US as a C Wrench (short for Crescent Wrench).

A.L.D. / ALD
Association of Lighting Designers.(UK)
ALD Website

A0/A1/A2/A3/A4/A5/A6 PAPER SIZES
A range of standardised paper sizes used worldwide in publishing and printing.
The sizes are part of the ISO216 standard.
A0: 841 x 1189mm (33.11 x 48.81 inches) [large scale drawings / plans]
A1: 594 x 841mm (23.39 x 33.11 inches)
A2: 420 x 594mm (16.54 x 23.39 inches)
A3: 297 x 420mm (11.69 x 16.54 inches) [twice an A4 page]
A4: 210 x 297mm (8.27 x 11.69 inches) [standard photocopy / document size]
A5: 148 x 210mm (5.83 x 8.27 inches)  [half an A4 page]
A6: 105 x 148mm (4.13 x 5.83 inches) [quarter of an A4 page - used for postcards / small booklets]
In the USA, the Letter size (216 x 279mm / 8.5 x 11 inches) is used instead of A4. 
Paper Sizes

A1
Lighting Industry Forum code which identifies the (original) recommended usage of different lamp types. A1 coded lamps are for use in projection. See also CP, T, P2, K.

AB
A technique used to record in stereo. Two (identical) microphones are placed next to each other, parallel to each other, and pointing in the same direction. As you're looking at the action, the one on the left is panned hard left on the mixer and the one on the right is panned hard right. There are some problems with this technique, such as reflections off each microphone, leading to comb filtering and also a narrow coverage. Some sound techs try to overcome the coverage problem by spacing out the microphones, although this can lead to 'muddy' sounds due to delays. See COMB FILTERING and XY.

AB POWERING
See PHANTOM POWER.

ABO
Association of British Orchestras.
ABO website

ABOVE
An actor move upstage (e.g. Clive moves above the chair).

ABSORPTION
The ability of a surface to absorp sound. The absorption coefficient of a material is a figure between 0 and 1, representing its degree of absorption.

ABSTRACT
A scenic or other design which is nonrepresentational and suggests the situation rather than simulating it. 

ABTT
The Association of British Theatre Technicians, which was formed in 1961 as a charity, to provide a forum for discussion among theatre technicians, architects and managers of all disciplines, and disseminate information of a technical nature, to all its members.
ABTT Website

AC
Short for ALTERNATING CURRENT. An AC cord or cable is used to connect between a mains power socket and a piece of equipment.
A range of different connectors are used to connect to the equipment. The 3-contact IEC cable is common in Europe, and is sometimes known as a Kettle Lead. A figure 8 cable is used on smaller equipment which is double-insulated and has just two connections. Powercon is used on heavier duty equipment and locks into place to prevent accidental disconnection. 

ACAPELLA
A sung performance which is not accompanied by musicians. (From the Italian A CAPELLA, meaning 'as in the chapel')

ACCENT LIGHTING
Lighting on a particular item or area on stage, to make it stand out or for aesthetic reasons, rather than to light an actor or functional area. Examples include lighting on specific architectural features on the set or in the theatre to make them 'pop' or because they're particularly significant. 

ACETONE
A flammable solvent used in some prop/costume-making processes. Used by make-up artists to remove skin adhesive from the netting of wigs and moustaches by immersing the item in an acetone bath, then removing the softened glue residue with a stiff brush. Also one of the primary components of some nail polish removers.

ACL / A.C.L.
Acronym for AirCraft Landing Light. See AERO.

ACN
Advanced Control Network. A new (2003) ethernet-based control protocol between control desk, dimmers & moving lights. Developed by ESTA and Strand Lighting. DMX nodes are used to communicate with non-ethernet devices.

ACOUSTIC PICK-UP
See PICK UP

ACOUSTICS
The behaviour of sound and its study. The acoustic of a room depends on its size and shape and the amount and position of sound-absorbing and reflecting material. The quality of sound in a given space, measured and analyzed by its clarity, loudness, liveliness, reverberance, echoes, dynamic range, envelopment, spaciousness, warmth and silence or noise control rating.

ACT
1) Subdivision between sections of a play. A short play is a 'One-Act-er', a play with one interval has two Acts etc. Acts are subdivided further into Scenes. 
2) The thing Actors can do which makes them different from Techies (!!).

ACT CHANGE
A change of either scenery, lighting, costume, props or other technical elements between acts of a play or musical. Theatres with little backstage space may have to reconfigure scenery stored offstage during the interval so that the next act runs smoothly.

ACT DROP
Victorian stretched framed and painted canvas. Used as a visual stimulation during scene changes, and to indicate that there was more to come (the end being indicated by the HOUSE TABS). There are believed to be only two operational today - an original one at Gaiety Theatre, Isle Of Man, and a 1996 reproduction at Her Majesty's Theatre, Ballarat, Victoria, Australia.
Term now used to refer to any front cloth or tabs lowered during intervals. Especially pantomime / musicals. 
In ballet, the act drop permitted pre-interval curtain calls to take place. 
Gaiety Theatre
Her Majesty's Theatre

ACTING AREA
That area within the performance space within which the actor may move in full view of the audience. Also known as the playing area
This term is also used to describe the smaller subdivisions of the main stage area which are lit separately by the lighting designer (e.g. 'The stage is split into 6 acting areas, 3 downstage and 3 upstage').
(Also the name of an early Strand down-lighting floodlight - it was called an Acting Area Flood, and was colloquially known as 'Ack Ack' or 'A.A.').

ACTING EDITION
Published copy of a script containing notes for the actor and technicians, often credited to the design team of the premiere production not necessarily the playwright.

ACTION PROP
A hand-held practical prop used by an actor for combat or for a specific purpose.

ACTION VEHICLE
A car / van / bus / other vehicle that takes part in a stunt during a film / TV shoot. See also PICTURE CAR.

ACTIVE
In electronics (particularly audio), an 'active' circuit operates with an external power supply and is usually low power, while a 'passive' circuit operates directly on the signal using the inherent power of the surrounding circuitry. 
This is why an active crossover is usually placed before the amplifiers, with integrated circuits and line level signal processing (100 Ohms impedance or greater), while a passive crossover acts after the amplifiers where the power level is much greater (16 Ohms impedance or less). Amp to speaker level is generally between 2 and 16 Ohms, while preamplifier electronics are generally 100 to 100K Ohms.
Submitted by Bruce Trotter

ACTOR
Person (male or female) whose role is to play a character other than his/her own. Although the term 'actress' is sometimes still used for a female actor, many women prefer to have the same title as the men.

ACTOR AUDIENCE RELATIONSHIP
There are many different theatre shapes and styles, but the most important factor when designing a space for performance is the relationship between the audience and the actors on stage. The audience should be able to clearly see and hear all of the actors on the stage, in order to have a connection or relationship with them.
A space where the audience is close to the stage (or feels close to the stage) is known as an INTIMATE auditorium.
If the space is too big, it's harder for the audience to feel involved in the performance. 

AD LIB
From Latin Ad libitum meaning "at one's pleasure".
The presence of mind by an actor to improvise when;
1) another actor fails to enter on cue
2) the normal progress of the play is disturbed
3) lines are forgotten
4) It may also be a bad habit developed by some actors whereby unnecessary "gags" are introduced into the dialogue.

In the past, any business or words that were not in the scripted act 'as known' would be seen as a breach of contract by some No.1 Managements. 

ADA
Acronym for Americans with Disabilities Act, which became law in 1990. It covers similar ground to the Disability Discrimination Act (DDA) which became law in 1995 in the UK. Both Acts are designed to outlaw any kind of discrimination against people with any form of disability. 
The acronyms ADA and DDA are used also to describe the amendments that are made to procedures, buildings and resources to comply with the Act. 

ADAM
See DIGITAL RECORDING.

ADAPTOR
1) Connector which allows two or more electrical devices to be connected to a single power outlet. The connection is normally parallel, that is, each device is fed the same voltage, but the current is divided between them. Sometimes known as a 'Twofer'. A three-way splitter is known as a 'Threefer'. A Series splitter is also available where a voltage is shared equally between two loads.
2) Also an ADAPTOR can be the same as a JUMPER.
See SERIES SPLITTER, JUMPER and GRELCO.

ADAT
See DIGITAL RECORDING.

ADB
(Manufacturer) Belgian manufacturer of lanterns, control desks and dimming equipment. Named after the initials of it's founder, Adrian de Backer.
ADB website

ADB 62.5
Near-obsolete digital lighting control protocol developed by ADB. Uses a 5 pin XLR connector but is NOT compatible with DMX512

ADDITIVE COLOR MIXING
See COLOR MIXING.

ADDRESS
(LIghting) Each item of equipment controlled by DMX512 has an address, which is the first DMX control channel to which it will respond. A dimmer rack requires 1 DMX channel per dimmer. A moving light requires many DMX channels.
For example, in a situation where you have three 6-way dimmer racks, the first should be addressed to 1, the second to 7 and the third to 13. Moving lights requiring 16 DMX channels each might be addressed to 120, 137, 154 etc.
The address is either set via pushbuttons (up / down) to get to the correct channel, or via a menu screen, or via small rotary selectors where you can set each digit of the address. 

ADJUSTABLE SPANNER
See A.J.

ADN
Advanced Dimmer Network. Networking protocol developed by ADB.
ADB website

ADR
Stands for Automated Dialogue Replacement. Also known as "looping" this is the post-production process on a film / TV shoot where actors re-record their lines after original filming, either because the original production sound was not up to standard or due to external factors (aircraft noise in a period piece) which weren't noticed at the time of filming. 

ADVANCE BAR
(UK) Lighting bar positioned just downstage of the proscenium arch. Also known as ANTE PROSCENIUM (from Latin 'Before' or "In Front').

AEOLIPHONE
More commonly known as a wind machine, this is a specialist musical instrument / sound effects generator used to produce the sound of a gusty wind. 
Video

AERIAL
Cable or rod used to send and receive radio signals (connected to transmitter and receiver or tuner).

AERIAL GOBO
A gobo projected from a moving light or profile which is focussed into the air above the stage or audience, in order to add atmosphere and dimensional texture through smoke or haze in the venue. 

AERO
A type of high intensity Par lamp that derives its name from its use as an aircraft landing lamp. The true Aero is 28V and 250W (type 4596), although there are many variations. The lamp has a very tight beam.

AES/EBU
Audio Engineering Society / European Broadcast Union. Digital audio transfer standard, similar to S/PDIF. Uses 3 pin XLR connectors.
What is AES/EBU

AESTHETIC DISTANCE
Aesthetic distance refers to the gap between an audience member's conscious reality and the fictional reality presented on stage. If the audience member becomes fully engrossed in the illusory narrative world of the drama, the director has achieved a close aesthetic distance. If the director then jars the audience member from the reality of the story, essentially reminding them they are watching a play, the director is said to have "violated the aesthetic distance." 

AETTI
Arts & Entertainment Technical Training Initiative (UK).

AGC
Automatic Gain Control. Circuitry within recording equipment which compensates for differences in volume in the incoming sound signal by adjusting the gain automatically. Helps to reduce wild swings in volume.

AGITPROP
The original sense of agitprop was "agitation and propaganda on behalf of Communism", or "a government agency or department responsible for agitation and propaganda". The main current sense of the word is simply "propaganda, especially socially or politically motivated propaganda appearing in literary works, films, etc."; though the word often refers to political propaganda, it is not restricted to communist doctrine. 
The word agitprop is first found in English sources in the mid 1930s.
From the Random House Word of the Day website.

AIFF
Audio Interchange File Format. Uncompressed Audio file format used on Mac systems. 
Digital Audio File Formats

AISLE
A passage through seating.

ALGINATE
An organic polymer which is a viscous gum found in the cell walls of brown algae. The commercial variety is extracted from seaweed. Supplied as a powder, when mixed with water it becomes a fast-setting mould-making material which is used to make casts of body parts or delicate prop items. The resulting mould is very detailed and strong. Dental alginate is used to make casts of teeth and gums. Take care to store the powder in an air-tight container as it's very absorbant and will 'go off' very rapidly if left open to the air.

ALPHAPACK
(Trade Name) Portable 3 way dimmer pack manufactured by Zero 88 in the UK. Integral faders to control the 3 dimmers. Maximum 6.3A load per dimmer. 
Zero 88 website

ALTERNATE
Alternative name for an Understudy who is hired to understudy a main role but also contracted to play that role in certain performances. See also STANDBY, SWING, UNDERSTUDY.

ALTERNATING CURRENT*
An electric current that reverses direction in a circuit at regular intervals. Abbreviated to AC. UK mains electricity is AC and changes direction 50 times per second (that is, the frequency is 50Hz).
See also DIRECT CURRENT.

AMATEUR
Member of a theatre company which is not professional.

AMBER DRIFT
A phenomenon seen when tungsten halogen lamps are dimmed which results in the light output becoming warmer (lower in COLOR temperature) as it becomes dimmer. LED lights maintain the same COLOR when dimmed, unless they have been designed to emulate the amber drift of tungsten light sources. 

AMBIENT LIGHT
The light in a venue with no stage-lighting sources switched on. Background light.

AMBIENT NOISE
The sound heard in a given room with no sound sources. Each space has a particular sound which aids our identification of the kind of space we're in.

AMDRAM
Short for Amateur Dramatics.

AMP
Abbreviation for ; 
1) AMPERE
2) AMPLIFIER

AMPERE
The standard unit for measurement of electrical current passing through a circuit (usually abbreviated to AMP). Written as 'I' in equations. Cables, fuses and switches are designated by their current carrying capacity. (Following phrase refers to UK standards). Square pin plugs are rated at 13 Amps maximum and Round pin plugs at either 5 Amps or 15 Amps maximum, depending on the size of the pins. If a cable rated at 5 Amps is used with a load of 15 Amps (for example), the cable will overheat and possibly catch fire.

AMPHITHEATRE
Circular or oval open-air theatre with a large raked seating area (often semi-circular) sloping down to the stage. Originates from ancient Rome where vast amphitheatres were built for spectator sports and games.

AMPLIFIER
Sound equipment that amplifies/boosts the low voltage, low current signal from a CD player, mixing desk etc. into a higher current signal suitable for driving speakers.
As a general rule, each speaker in a sound system requires a separate amplifier. Each amplifier unit usually contains two amplifiers (for the two stereo components (left and right) of the sound signal), so with a single amplifier box, you can drive two speakers.
See POWER AMPLIFIER, CROSSOVER.

AMPLITUDE
The strength of a vibrating wave; in sound, the loudness of the sound.

AMX
Powerful programming language with allows you to control a wide range of audio-visual equipment using simple interfaces (push buttons or touch screen). Widely used in complex audio-visual installations.
AMX website

AMX-192
See MULTIPLEXED SIGNAL.

ANACHRONISM
A scenic item, prop or costume which is from a different time period than that being portrayed on stage. Usually, it's a modern item that shouldn't be seen in a period piece. 

ANAGNORISIS
Anagnorisis is a moment in a play or other work when a character makes a critical discovery. 

ANALOGUE SIGNAL
A continuously variable signal that can have any value over a given range. 
1) In lighting: an analogue voltage within the range 0 to 10 Volts can have values of 0, 2, 8.785 or any value between. Most dimmers require an analogue voltage in order to operate (from 0 to -10V or 0 to +10V depending on the manufacturer). Most lighting control desks produce a digital multiplexed output, which is converted by a demux box to an analogue signal for the dimmer. See also Digital dimmer. 
2) Sound: An analogue recording will record the exact waveform of the original sound, simply converting it to an electrical signal at the microphone, and back into air movement at the speaker. See DIGITAL.

ANGEL
One who privately finances a production, usually often with several other backers; their identity is traditionally kept private. May be an individual or a company. 
See also PRODUCER.

ANGSTROM
Unit of measurement of length (e.g. for wavelengths of light). 1 Angstrom is equal to one ten billionth (1 x 10^-10) of a metre. The unit is named after the Swedish physicist Anders J. ?ngstr?m. 
See WAVELENGTH.

ANILINE DYE
A type of deep penetrating natural dye originally made from coal tar. Water-based or alcohol-based dyes are available. As the product will stain anything it comes into contact with, protective gloves and eye protection should be used.

ANIMATEUR
(From French) Facilitator of a community, education or group event (social, cultural or artistic). The Animateur may be a group leader, or may have initiated a project. She or he is responsible for running the event.

ANIMATION DISC
See EFFECTS.

ANIMATRONIC
Originally Audio-Animatronic™, this term describes a robotic figure, particularly in a theme park environment or on a movie set, which is able to repeat a limited range of pre-programmed functions, typically in synchronisation with a pre-recorded soundtrack. The term now describes a character controlled either electronically by radio remote control, or by cable/lever controls. 

ANNOUNCER
In seventeenth century theatre and street performances, the Announcer would greet the audience, and give the play some context, either in terms of political or social background, or just to fill in some background detail to help the audience understand. 

ANSI / A.N.S.I.
American National Standards Institute. Three letter ANSI codes are used in the US to identify lamps.
ANSI website

ANTAGONIST
The opposite of the PROTAGONIST in a drama. 

ANTI PROSCENIUM
Originally Ante Proscenium, meaning in front of the proscenium.
See ADVANCE BAR.

ANTI RAKE
The act of modifying furniture or props by shortening the upstage legs etc. so that they can stand level on a raked stage. Known as COUNTER RAKE in the US. See also Raked Stage.

ANTISTROPHE
The second section of an ancient Greek choral ode or of one division of it. 

APOLLO DESIGN TECHNOLOGY
(Manufacturer) US-based manufacturer of gel, gobos, effects and scrollers.
Apollo Design Technology Inc. website

APPLAUSE
Applause (Latin applaudere, to strike upon, clap) is primarily the expression of approval by the act of clapping, or striking the palms of the hands together, in order to create noise. Audiences usually applaud after a performance, such as a musical concert, speech, play or a performance to mark the sign of enjoyment and approval. Audience members clap their hands at random to produce a constant noise; however, it tends to synchronize naturally to a weak degree. As a form of mass nonverbal communication, it is a simple indicator of the average relative opinion of the entire group; the louder and longer the noise, the stronger the sign of approval. (from Wikipedia)

APPLE BOX
A small strong wooden box used as a temporary step or to lift an item (or actor) up to make it visible. Named after the standard-sized fruit packing crate. Used in the motion picture industry.
More about Apple Boxes

APRON
The Apron is a section of the stage floor which projects towards or into the auditorium. In proscenium theatres, it's the part of the stage in front of the house tabs, or in front of the proscenium arch, above the orchestra pit. Also known as Forestage.
If an apron stage extension is added to an existing traditional proscenium arch theatre, this often results in poor sight lines from seats that are higher in the auditorium, leading to audience members having to lean forward in an attempt to see.
German: vorbühne (literally, forestage). 

ARBOR
US equivalent of CRADLE in a counterweight flying system.

ARC LIGHT
See DISCHARGE LAMP.

ARCHITECTURAL LAMP
A type of linear filament lamp with contacts at 90 degrees to the filament which can gives the appearance of a continuous line of light (similar to neon, but dimmable).

ARCLINE
(Trade Name) A COLORed plastic tube containing a number of small strobe units which, when triggered, flash in sequence down the tube. Many tubes can be connected together.

ARENA
Form of stage where the audience are seated on at least two (normally three, or all four) sides of the whole acting area.
See END ON, THRUST, IN THE ROUND.

ARIA
A solo performance in an opera used to highlight the emotional state of the main character(s).

ARMOURY
The Department in a large producing theatre which deals with the maintenance and storage of prop weapons.

ARRANGEMENT
The arrangement of a piece of music defines how it will be performed, and how it will sound. It covers which musical instruments will play each part of the melody and harmonies. The score for a piece of musical theatre may have arrangements for a small (school) band, or a large Broadway orchestra. 

ARRAY
A set of loudspeakers flown in a performance space. See also CLUSTER.

ARRI
(Manufacturer) German/US manufacturer of film lighting and cameras (Arriflex). Founded in 1917. Previously, Arri made a range of lighting desks (including Imagine, Impulse, Mirage, Microlux) which were early versions of desks now produced by ETC. ETC took over the lighting control side of Arri in 1995.
ARRI website

ART-NET
Ethernet-based lighting control protocol, developed by Artistic Licence. ArtNet can carry up to 256 DMX512 universes on the ethernet saving on cable runs. With the development of wireless networking the possibilities are endless.
Art Net website

ARTIC
Short for Articulated Lorry. Lorries of 40 feet length (or more) are used to transport sets, costume, props and sound & lighting equipment from venue to venue. A number of companies specialise in moving theatrical and musical tours around the country / world.

ARTISAN
(Trade Name) Moving light control console made by Vari*Lite.
Vari*Lite Website

ASCAP 
The American Society of Composers, Authors and Publishers is a not-for-profit performance rights organisation that protects its members' musical copyrights by monitoring public performances of their music, whether via a broadcast or live performance, and compensating them accordingly.
ASCAP website

ASIDE
Lines spoken by an actor to the audience and not supposed to be overheard by other characters on-stage.

ASM
Assistant Stage Manager.

ASPECT RATIO
A ratio which defines the relationship between the height and width of a movie frame.
The Academy ratio is 1:1.375 (i.e. if the height of the image is 1 unit, the width will be 1.375 units).
Silent movies were shot in 1:1.33.
Cinemascope is 1:2.35.
A traditional TV picture is known as 4:3 (width:height, which can be expressed as 1.33:1). A widescreen TV is 16:9. (or 1.77:1)

ASSISTANT DIRECTOR
Assistant to the Director - works on specific tasks, sequences etc. to lighten the workload of the Director.

ASSISTANT STAGE MANAGER
Usually shortened to ASM, the assistant stage manager is the most junior member of the Stage Management team, and is often in charge of sourcing and running Properties during the run of a show. She or he is also a member of the stage 'crew'. See also STAGE MANAGER and DSM.

Association of Sound Designers
UK & international organisation representing the interests of sound designers and technicians. 
Association of Sound Designers website

ATAEA / A.T.A.E.A.
Australian Theatrical and Amusement Employees Association. Union for Australian theatre technicians, now part of MEAA. See BECTU and IATSE for the UK and US equivalents.

ATMOSPHERE
The normal background sound at any location.

ATTENUATE
To reduce the intensity of a sound signal. This is what the 'PAD' switch does on a sound desk.

ATTRIBUTES
The controllable parameters of a COLOR-changing or moving light are known as the ATTRIBUTES.
All moving lights will have pan & tilt, with many having COLOR wheels, gobo selection, gobo rotation etc. as additional attributes. LEDs can operate in a number of modes, based on the number of COLOR sources they have, as well as whether certain parts of the beam can be separately controlled. 

AUD
Abbreviation for Audience, used frequently in Iconic Productions. See AUDIENCE, SELECTED AUDIENCE MEMBER.

AUD-M
Abbreviation for Audience member.

AUDIENCE
Person(s) attending a performance. The audience sit in the auditorium or arena with a view of the stage. 

AUDITORIUM
The part of the theatre accommodating the audience during the performance. Sometimes known as the "house". From the Latin Audio - "I hear".

AUGMENTED REALITY
Augmented reality (AR) is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated sensory input such as sound, video, graphics or GPS data. It is related to a more general concept called mediated reality, in which a view of reality is modified (possibly even diminished rather than augmented) by a computer. As a result, the technology functions by enhancing one’s current perception of reality.

AUTOCAD
Industry-standard CAD program for architects and designers. WYSIWYG contains a cut-down version of Autocad, along with visualisation tools.

AUTOMATED FIXTURE
See MOVING LIGHT.

AUTOMATIC STOP
Many reel-to-reel tape players for theatrical use have a facility that stops the tape mechanism when a piece of clear leader passes a detector adjacent to the erase head. This can be used to cue the tape up ready to start the next effect.

AUTOMATION
1) Facility available on larger sound mixing desks allowing channel muting or even fader moves to be taken under the control of a computer to ensure accurate and repeatable mixing. 
2) Describes the method used instead of stage crew for moving bits of set around shows with a big budget. See MOUSE, SPADE.

AUXILIARY INPUT or RETURN
A route back into the sound desk for a line level signal sent to a piece of outboard equipment (usually effects processor / EQ unit etc.) via an auxiliary send.

AUXILIARY OUTPUT or SEND
An additional line level output from a sound desk which can be used for foldback or monitoring without tying up the main outputs. Each input channel will have a path to the Aux buss. Also used for feeding a signal to an effects processor. See Auxiliary Return.

AV
Short for Audio-Visual, referring to projected or screened video or textual material. 

AVAB
Swedish lighting equipment manufacturer. 
Also, AVAB can refer to a digital lighting control protocol developed by the company. It's slower than DMX512 but still in use. It often uses a 5 pin XLR connector, but is NOT compatible with DMX512.
AVAB website

AVANT-GARDE
French term used in English as a noun or adjective to refer to people or works that are experimental or innovative (literally, 'ahead of the guard'). As experimental techniques have been adopted by mainstream theatre, the boundaries which define the avant-garde are constantly shifting. 
Wikipedia entry

AVISTA / A VISTA
A change of setting / scenery unhidden from the audience. This technique is increasingly popular due to modern advances in scenic automation, where entire set changes can be accomplished in seconds.

AVOLITES
(Manufacturer) UK-based manufacturer of lighting control consoles (Azure, Pearl, Sapphire, Diamond) and dimmers.
Avolites website

AWG
American Wire Gauge. US system for measuring the thickness of wire. The lower the number, the thicker the wire.

AWG
Australian Writers' Guild.
AWG website

AXIS
(plural AXES). An individually controllable moving element controlled by a scenic automation or powered flying system. For example, a system controlling three flying pieces will have three axes of automation. 

D54
See MULTIPLEX.

DAIS
A low raised platform or stage for several people, above the rest of the stage area.

DAISY-CHAINING
Connecting items of equipment together by linking from one to the next in a chain. Used for connecting demux boxes to dimmers etc.

DANCE CAPTAIN
Member of a group of dancers in a show who is responsible for leading rehearsals and warm-ups prior to the performance.

DANCE FLOOR
1) A vinyl floor covering, usually kept on a plastic or cardboard tube, which is rolled out and taped to the stage floor to create a surface suitable for dance. Dance floor should be left to adjust to room temperature before being taped otherwise it will not lay flat. Many different types of floor are available, including different colors and degrees of cushioning, and the product may be known by it's manufacturer's name (e.g. Marley Floor, Harlequin Floor).
2) A wooden floor which is either naturally springy or has been constructed with rubber pads under it which absorb impact, and create a surface which performers are able to jump on without damaging knees or other joints, as the floor absorbs the impact.
German: Tanzteppich

DANCE LIGHTING
Lighting design for Dance is reliant on a great deal of sidelight from BOOMS at the side of the stage. There are normally at least three lanterns on each boom, and three heights - SHINS (to light feet and lower legs), MIDS and HEADS.

DANCER
Member of the company whose role is choreographed, and who has no spoken words.

DARK
A venue that has been closed to the public. Some theatres go dark temporarily during production periods, when the next show is in preparation on stage. To keep the audience (and their money) coming in, some venues show films or have other activities not involving the stage.

DARK RIDE
A themed attraction taking place in an indoor environment where the ride designers have total control over light and sound. Often incorporates a mechanical ride system to move the guests through the attraction at a known rate, and may also include special effects and animatronic elements. 
More about Dark Rides

DAT (Digital Audio Tape)
See DIGITAL RECORDING.

DATA PROJECTOR
As prices are dropping, the use of a data projector connected to a laptop or PC/Mac is within the budget of almost every performance.
See link below for more information. 
Known in parts of Europe as a BEAMER.
See Multimedia Projection for Drama for more information.

DAYMAN
A member of the backstage staff who is hired or paid by the day, for the specific hours worked. Prefixed by the appropriate technical area (e.g. Stage Daymen, Electrics Dayman / LX Dayman etc). May also be required to work shows (Show Dayman). 

DEBRIEF
Following a rehearsal (or an early performance in a run) the director/producer/actors captain or a senior supervisor will give notes to the cast and crew about where to make changes, improvements, cuts etc.

DÉNOUEMENT
The moment in a drama when the essential plot point is unravelled or explained. (e.g. "So you see I couldn't have killed the gardener. Because I AM the gardener" (Loud organ music etc.)).

DBO (Dead Blackout)
See BLACKOUT.

DBX
A tape-recording noise reduction process.

DC
Short for DIRECT CURRENT.

DCC
(Digital Compact Cassette) Manufactured by Philips in the Netherlands, this format was supposed to be the successor to the compact cassette, but Mini Disk won the marketing war. DCC was discontinued for mass market use in 1996. See DIGITAL RECORDING.

DDA
Acronym for the Disability Discrimination Act (DDA) which became law in 1995 in the UK. It covers similar ground to the Americans with Disabilities Act, which became law in 1990. Both Acts are designed to outlaw any kind of discrimination against people with any form of disability. 
The acronyms ADA and DDA are used also to describe the amendments that are made to procedures, buildings and resources to comply with the Act. 

DE-RIG
The process of removing lanterns & cabling from flying bars or grid - returning the venue to it's normal state, or as preparation for the next production.

DEAD
1) A pre-plotted height for a piece of scenery or lighting bar - 'that bar's on its dead'. The positional indicators on the rope (either PVC tape, or more traditionally cotton tape passed through the strands of the rope) are called DEADS. Sometimes flying pieces are given a number of extra deads, that may be COLOR coded, in addition to the 'in dead' (lower) and 'out dead' (higher - out of view). In the US, TRIM has the same meaning. Fluorescent ribbon is often used, through the fibres of the rope. The fluorescent COLOR shows very clearly under UV light, which is often used to light fly floors. 
2) Scenery or equipment not needed for current production - 'that table's dead'.
3) An electric circuit that has been switched off or has failed - 'the circuit's dead, you can change the lamp now'
Submitted by Chris Higgs

DEAD HANG
A rigging point direct to the grid / beams above the stage, not to a flying bar.

DEAD HINGE
A hinge used as a right-angle bracket.

DEAD LINE
A static suspension, 'drop wire' or bracing line. A suspension without any lifting power.
Submitted by Chris Higgs

DEAD MAN
Also known as DEADMAN'S BUTTON (DMB). This is a handle that has to be squeezed by a technician in order for a pre-programmed automation sequence to take place. If for any reason the relevant technician is not in position, the system does not allow the sequence to run. 

DEAD OUT
To replace a hoist or winch suspension with a dead line. Once the truss or piece is at trim, to tranfer the load onto 'dead lines' and remove the hoists or lifting devices.
Submitted by Chris Higgs

DEAD ROOM
A room with very thick sound absorbers, causing a very dull sound with no reverberation.

DECIBEL (dB)
Relative measurement for the volume (loudness) of sound. One dB is the smallest variation in loudness that the human ear can detect. Also used to measure the difference between two voltages, or two currents. See ZERO DB.

DECK
1) Stage/Rostrum Floor (e.g. "Fly that flat in to the deck") [known in German as bühnenboden]
2) Tape deck/Record deck.
3) A steel-framed platform with a wooden top used with replaceable scaffold legs (Trade names include Steeldeck, Metrodeck (made by Maltbury), ProDeck).

DECOR
See SET DESIGNER.

DELAY
Outboard sound equipment that can momentarily stores a signal being sent to part of a P.A. system so that delayed reinforced sound reaches the audience at the same time (or just after) the live sound from the stage. Using the 'Haas Effect' the audience cannot detect the sound as amplified.

EARTH LOOP
Normally refers to audio interference resulting from a situation where two pieces of sound equipment are connected together over a long distance. The earths of the equipment are at different potential, and this results in an audible hum or buzz. Can be cured by removing the screen connection on one end of the signal cable. Electrical earth connections must never be removed.

EARTH SPIKE
Copper rod inserted into the ground to maintain earth continuity (especially when using generators etc.)

EARTHING
Electrical safety requirement that metal parts of electrical equipment are connected to a common earth or ground point so that in the event of a fault, excess current can be carried away, causing the fuse to blow. Known in the USA as Ground. Some sound problems (such as hums) can be cured by altering the earthing / grounding arrangements of the system, but this should never involve removing the earth connections to equipment, only by adding an earth connection where none exists, or by adjusting the way audio cables are wired. Seek professional advice to avoid safety problems.

ECHO
A repeated sound received late enough to be heard as distinct from the source. See REVERB.

EDISON PLUG
Standard domestic power connector in the USA - a plastic body with two parallel metal contacts.

EDISON SCREW (ES)
Circular threaded lamp holder which is one of the standard fittings for domestic light bulbs. Other common types are BC (Bayonet Cap) and SES (Small Edison Screw). GES (Giant Edison Screw) is used for large wattage lamps.

EDM
Acronym for Electronic Dance Music. Repetitive beats and an awesome light show. 

EDUCATION DIRECTOR
Member of the theatre staff who develops work for schools, or provides resources on current productions and runs workshops for students / school groups.

EFFECTS PROJECTOR
Lantern used to project the image from a rotating glass effects disc. Used with an objective lens to produce the desired size of image. Commonly used discs are clouds, flames and rain.
See also: Lighting Effects

EFFECTS, LIGHTING
Animation Disc: A slotted or perforated metal disc which rotates in front of a lantern to provide 'movement' in the light. Most effective when used in front of a profile carrying a gobo.
Effect Disc: A painted glass disc rotating in front of an effects projector with an objective lens to focus the image (eg Flames, Rain, Snow).
Flicker Flame: Irregularly slotted rotating metal disc through which light is shone onto a prism-type piece of glass which scatters the beam of light and adds the 'dancing' effect of firelight to a scene.
Gobo Rotator: Motorised device inserted into the gate of a profile lantern that can be remotely controlled to rotate a gobo, usually with variable speed and direction.
KK Wheel: Slotted metal disc which rotates in front of a lantern to break up the light and provide movement. (Flicker Wheel)
Lightning: Created through the use of strobe sources or LED floods. Photoflood lamps were used in the past, but have a very short life, and aren't as bright as the other options.
Tubular Wave Ripple: Horizontal linear lamp around which a slotted cylinder is rotated providing a rising light (as reflected from water onto the side of a ship).

See also: Pyrotechnics
Lighting Effects
Fog, Smoke & Haze On Stage

EFFECTS, SOUND
1) Recorded : Often abbreviated to FX. There are many sources for recorded sound effects, from Compact Discs, to downloading from the internet. May form an obvious part of the action (train arriving at station) or may be in the background throughout a scene (e.g. birds chirping).
2) Live : Gunshots, door slams, and offstage voices (amongst many others) are most effective when done live.
See Door slam, Thunder Sheet, Rain box.
See also Compressor, Digital Effects, Exciter, Noise Gate, Reverb.

EGGS
Slang term used for Strand Pattern 123's, due to their shape.
Strand Archive

EIGHT ASPECTS OF THEATRE
Refers to a book entitled The Theatre of Bertolt Brecht: A Study from Eight Aspects by John Willetts (1959). The eight aspects of Brecht's work that are analysed in the book are:
1) The Subject Matter
2) The Language
3) Theatrical Influences
4) The Music
5) Theatrical Practice
6) The Theory
7) Politics
8) The English Aspect.

EKKYKLEMA / ECCYCLEMA
(Greek) Moveable platform used to move items on and off the Greek stage. The forerunner of the modern WAGON or TRUCK.

EL WIRE
Electro-luminescent Wire. Requires an alternating current power supply of between 90-120 volts, but this is usually generated by an oscillator circuit powered by a few AA batteries. The wire is very efficient and robust. The weak points tend to be the connections between the wire and the power supply, so ensure these are well-protected if the wire is being used in/on a prop or costume. 

ELECTRET MIC
A condenser microphone where the capacitor plates are given a charge during manufacture which they retain, therefore requiring no external power supply.

ELECTRIC
In the US, LX bars are ELECTRICs bars.
LX1 in the UK (first bar upstage of the proscenium arch) is FIRST ELECTRIC in the US.
In the UK, the bars front-of-house (audience side of the proscenium arch) are usually given names (e.g. Advance Bar, Front Perch, Circle Front) and upstage of the proscenium are numbered, with LX1 as the most downstage. 

ELECTRICS
See LX.

ELEVATION
A working drawing usually drawn to scale, showing the side view of a set or lighting rig. See PLAN.
In the US, the term "elevation" refers to a Front elevation. A Rear elevation shows backs of scenic elements. A side view of a set is known as a "section".
See also PAINTERS' ELEVATION.

ELEVATOR STAGE
A type of mechanised stage which has sections that can be raised or lowered.

ELLIPSOIDAL
A profile lantern with an elliptical reflector and at least one lens. Also known as an ERS (Ellipsoidal Reflector Spotlight).
A common type was the LEKO, made by Strand, but this has been eclipsed by the Source Four range, made by ETC.

EMERGENCY LIGHTING
A self-contained lighting system for a public space that provides enough illumination for the public to leave the area and to locate exits in the event of a power cut.
Emergency Lighting systems should be checked regularly (as required by local licencing authorities).
It's especially important to consider power cuts when using non-theatre spaces (especially outdoor spaces) for performances. 

EMERGENCY STOP
Also known as E-STOP, all scenic automation or powered flying systems have an emergency stop facility built into them. The pressing of any e-stop button in the system will immediately halt any movement and prevent any further movement until the system is reset. 

EMF
Abbreviation for Electromotive Force, or VOLTAGE.

ENCODER WHEEL
A flat disc with an indentation used to control certain functions of (often) moving lights on a lighting control desk. 

ENCORE
An extension of the performance due to audience demand. This usually applies to music concerts or stand-up comedy shows, where the performer will have an extra song or routine ready if there is a lot of applause. From the French which means "again" or "more".

END ON
Traditional audience seating layout where the audience is looking at the stage from the same direction. This seating layout is that of a Proscenium Arch theatre.
Also known as Proscenium Staging.
The end-on stage can be split into 9 areas: upstage right, upstage CENTER, upstage left, CENTER stage right, CENTER stage, CENTER stage left, downstage right, downstage CENTER, downstage left.
See also THRUST, IN THE ROUND, TRAVERSE.

ENHANCER
Sound processing equipment which increases the presence of the vocal track in a mix by adding to the treble information in the signal. Also known as an Exciter.

ENSEMBLE
An acting group. Normally used to describe a group of actors who work well together, with no-one outshining the others. A performance where the emphasis is on group work, and there are no star performers, is an ensemble performance. 

F.B.O.
Abbreviation for Fade to Blackout.

FACING
*to be defined

FADE
A fade is an increase, diminishment or change in lighting or sound level.
A snap fade is an instant change. A slow fade could be anything from 5 seconds to a few minutes (or even more, for a naturalistic sunset lighting effect). A quick fade is a couple of seconds long.
A fade out takes the lighting state to blackout (or a particular sound to silence). A fade in does the opposite.
A crossfade smoothly transitions from one state to another, without going through darkness (or silence for sound). 

FADE DOWN
A slow dimming of the lights to a lower level, but not all the way to blackout. See also FADE OUT.

FADE OUT
A slow dimming of the lights, ending in blackout. See also FADE DOWN.

FADE TIMES
On computerised memory lighting control desks, a lighting fade can have two times - an up fade and a down fade. The Up fade time refers to the time it takes dimmer levels to rise to their new positions. The Down fade time refers to the time for dimmer levels falling to their new positions.

FADE UP
An increase in lighting or sound level, over a given time period. An increase in level from an existing state is known as a BUILD.

FADER
A vertical slider which is used to remotely set the level of a lighting or sound channel.

FALLING ACTION
The events in a play that occur after the climax has been reached, but before the final part. 

FALSE PERSPECTIVE
A scenic design technique that makes a building or set appear larger than it actually is. The scale of objects that are supposed to be further from the observer is reduced to make them appear further away, even if they're not.

FALSE PROSCENIUM
A temporary frame formed by scenic canvas or vertical flattage within the proscenium arch. Used to reduce the size of the opening when putting a small set onto a large stage.
See PROSCENIUM ARCH.

FALSE STAGE
A special stage floor laid for a production. For example to allow trucks guided by tracks cut into this false floor, to be moved by steel wires running in the shallow (2 or 3 inch) void between the false floor and the original stage floor. A false stage is also required for putting a revolve onto a stage.

FAR CYC
(US) Lighting instrument used to light cycloramas or drops (see also CYC FLOOD).

FARCE
Form of comedy play originated in France, using fast-paced physical action and visual comedy more than humour based on language.

FARM
In certain Russian-speaking countries, FARM is used to mean Truss. (So Back Farm is Back Truss). 

FAT FINGER
A common problem among lighting & sound operators, when two buttons are accidentally pressed at the same time by a finger that's too large for the buttons. 

FAZER
A combined fogger and hazer, which can produce thick or thin smoke / haze. 

FEED
1) A power supply to a piece of equipment or installation is termed a 'feed'. Sound equipment and sensitive computer equipment should have a clean feed - that is, a supply that is free from interference from other equipment.
2) A signal from one system to another is also known as a feed (for example, an audio signal from the FOH desk to a TV company videoing a concert is known as a feed. A video relay of the conductor to screens in the wings is known as a Conductor Feed, etc.)

FEEDBACK
(Automation) Process by which information about the position of a piece of scenery is fed back into an automation system to ensure it's running correctly.

FEEDBACK / HOWLROUND
(Sound) A loud whistle or rumble heard emanating from a sound system. It is caused by a sound being amplified many times. (E.g. a sound is picked up by a microphone and amplified through the speaker. The microphone picks up this amplified sound and it is sent through the system again). Feedback can be avoided by careful microphone positioning, and can be reduced by use of Equalisation to reduce the level of the frequency band causing the feedback.

FEEDER
In the US, a main power cable to an installation is known as a feeder.

FEL
ANSI standard 1000W lamp, with a G9.5 medium 2 pin base, and is made by a number of manufacturers including GE, Osram, Ushio, Eiko and Philips.

FERRULE
The metal sleeve used to form an eye termination in steel wire rope which is pressed onto the rope under pressure from a hydraulic tool. Usually made from aluminium alloy, copper or steel.
Submitted by Chris Higgs

FESTOON
1) See Swag 
2) Describes tabs which adopt a sculpted shape. 
3) A length of cable incorporating a number of lamp holders used for outdoor party lighting etc. Available in multi-circuit form so that the lamps can be 'chased'.

FEV
Short for French Enamel Varnish, a stain which is a mixture of shellac and dye, diluted in methylated spirit.

FIBRE FRAME
A COLOR frame made from heat resistant fibres, which doesn't get as hot to the touch as a standard metal frame.

FIBRE OPTICS / OPTICAL FIBRE
A method of directing light down a very thin glass fibre. Fibre Optics are used mostly in communication, but find theatre applications in star cloths which are black backcloths with the ends of optical fibres poked through, to create a mass of pin pricks of light. A large bundle or harness of fibres may be fed from one light source, sometimes with a motorised COLOR or flicker wheel. 
New technology enables digital sound signals to be sent down optical fibres, replacing heavy and expensive multicore cables.

FIELD
Refers to the spread of light intensity across a beam. Most profile lanterns have an adjustable field. A Flat field has an even distribution, a peak field has a 'hot spot' in the CENTER of the beam. A flat field is essential when using gobos. See Profile.

FIFTH BUSINESS
Now obsolete term for an actor who is neither the hero, heroine, villain or confidante in a traditional drama, but is nonetheless essential for revealing important plot points. She/he is known as Fifth Business.

FIGHT CALL
A warm-up and rehearsal of fight choreography held before each performance.

G-CLAMP
Ironmongery fitting for clamping two items into position together. See also Hook Clamp.

GAC-FLEX
A spanset with a metal wire running through it instead of a nylon core.  
GAC stands for Galvanised Aircraft Cable.

GAFFER TAPE / GAFFA TAPE
Ubiquitous sticky cloth tape. Most common widths are .5 inch for marking out areas and 2 inch (usually black) for everything else. Used for temporarily securing almost anything. Should not be used on coiled cables or equipment. Originally known as Gaffer's Tape, from the Gaffer (Master Electrician) on a film set. Also known as Duct Tape. See PVC Tape.

GAIN
1) The level of amplification given to a signal or of a system.
2) A control of the amount of pre-amplification given to a sound signal on its way into a mixer. Particularly important for microphone inputs - a quiet vocal will require a lot of gain, a loud singer less so.

GAIT
The gait is the way an actor (or anyone) walks. 

GAK
(US slang) Anything on stage that isn't of interest to the technical staff (e.g. music stands, chairs, water bottles).

GALAXY
(Trade Name) Large computerised memory lighting desk. Previously manufactured by Rank Strand (now Strand Lighting)
Strand Lighting website
Strand Archive

GALLERY
1) One or more raised seating platforms towards the rear of the auditorium.
2) See LOADING GALLERY.

GAM
(Manufacturer) USA based manufacturer of lighting gels, gobos and accessories. GAM stands for Great American Market. See COLOR FILTER, GOBO.
GAM website

GANTRY
A walkway at high level inside a building. 

GAS TABLE
Distribution point for gas used in theatre lighting (from around 1816 - 1890). Various valves and wheels controlled the flow of gas from the central point to each part of the stage, so that by using a team of people, complex lighting fades could be achieved, before the advent of electricity for lighting. According to Richard Pilbrow (Stage Lighting Design: The Art, The Craft, The Life 1997) the gas table was the first stage lighting switchboard.

GATE
1) The point of focus in a profile spot where the shutters are positioned and where an iris or gobo can be inserted. 
2) A single base section of a folding rostrum system. 
3) See NOISE GATE.

GAUZE
Cloth with a relatively coarse weave. Used unpainted to diffuse a scene played behind it. When painted, a gauze is opaque when lit obliquely from the front and becomes transparent when the scene behind it is lit . Many different types of gauze are available;
Sharkstooth gauze is the most effective for transformations, because it is the most opaque.
Vision gauze is used for diffusing a scene and for supporting cut cloths.
Holo-Gauzeâ„¢ is a metallised gauze optimised for front projection holographic illusions.
Also known as a Scrim.
Holo-Gauze
See also Lighting With A Gauze / Scrim

GEL or Gelatine
See COLOR FILTER.

GEMINI
(Trade Name) Medium size computerised memory lighting desk with 180 channels. Previously manufactured by Rank Strand (now Strand Lighting)
Strand Lighting website
Strand Archive

GENDER CHANGE
As audio connectors are usually referred to as male or female versions, a gender changer is used to change a male connector to a female etc. 

GENERAL COVER
Those lanterns in a rig which are set aside purely to light the acting areas.
The stage is normally split into a number of areas for this purpose, which can then be isolated or blended together as required by the director. ~
See Special.
Designing and Focussing a General Cover

GENERATOR
Fuel-powered engine which drives a dynamo to convert mechanical energy into electricity. Also known as a GENNY. 
Generators are used as back-up power supplies in the event of failure of the mains electricity, or to supplement the power available in a venue for a specific show that requires a large amount of electrical power.
Also used on outdoor events to provide all power (including sound system, lighting rig, catering, emergency lighting etc). A large event will have a number of generators and back-up generators to power different zones of the site. 

GENERIC
Standard stage lighting instruments, rather than moving lights or other effects. (e.g. 'There are 40 instruments in the rig - 20 moving lights and 20 generics'). 

GENIE
(Trade Name) A range of mobile access platforms or lifting devices with either hand-cranked or compressed air lifting mechanisms.
Genie Industries website
Access Equipment

GENRE
A style of performance - a way of categorising different types of drama.

GERB
See PYROTECHNICS.

GERMAN MASKING
See MASKING.

GESTURE
Body or facial movements of a character during a play. Gesture can be described by the author, or suggested by the director or actor.

GET-IN
The process of moving set, props and other hardware into a theatre prior to the fit-up. (aka LOAD IN (US) and BUMP IN (Aus.) and PACK IN (NZ.))

GET-OFFS
A means for an actor to get off a rostrum, high level etc. out of view of the audience. Usually treads. Also known as ESCAPE STAIRS

GET-OUT
Moving an entire production out of the venue, and back into storage or into transport. Usually preceded by the strike (where the set is disassembled back into component parts.
The Get Out is also known as Load Out (USA) or Bump Out (AUS.) or Pack Out (NZ).

GFI / G.F.I.
(US) Ground Fault Interruptor. See RCD.

GHOST LIGHT
(US) A light left burning overnight on stage to keep friendly spirits illuminated and unfriendly spirits at bay. Also believed to keep the theatrical muse in a 'dark' theatre, and to stop people tripping over bits of scenery when they come into the theatre in the morning.
The ghost light consists of a vertical pole with a bare light bulb on it, and is placed on stage. Care should be taken that the cable doesn't create a trip hazard, and that the light bulb is protected with a metal cage. 
The type of bulb is not critical - it should be chosen so that enough light is emitted to enable people on stage to see furniture / other items to stop them tripping over. Where possible an energy-saving lamp should be used. 
Also known as the 'Equity Light'. See link below for more information.
Could also refers to the light emitted by a lantern when a dimmer has not been 'trimmed' correctly, and is leaking.
More information about Ghost Light

GHOST LOAD
A lamp plugged into a dimmer which is also being used to dim an inductive load (e.g. transformers) rather than a resistive load (filament lamps). Most dimmers (and certainly all cheap dimmers) are designed for resistive loads, so adding a load lamp onto each dimmer circuit that's not being used for resistive loads enables the dimmer electronics to work correctly.
A ghost load is also used to increase the load on a dimmer when using very low wattage equipment. The ghost load is positioned next to the dimmers out of view of the audience and connected via a parallel splitter (e.g Grelco). 
Also known as a LOAD LAMP. 

GHOSTING
A method of determining the exact position of a followspot's beam by faintly exposing it on a darker area of the stage or upon the drapes. Often done just before a 'pick up' so the operator can have the lantern aimed and ready. A more professional practice is to use sights to line up a followspot.
Submitted by Jayson Bowles

GLASS FIBRE
A combination of a glass mat and a resin which can be formed into a strong shell. Used in prop-making.

GLASS GOBO
A highly detailed gobo consisting of an aluminium pattern sandwiched between two thin pieces of glass. A glass gobo is more expensive than a standard steel gobo, and requires special handling. A glass gobo holder must be used which allows the glass to expand when heated. When used in lanterns more powerful than around 650W, the lamp should be preheated before being turned to full to warm up the gobo, otherwise the thermal shock may cause the glass to crack. 

GLAZE
Glossy finish applied as a final coat to a painted stage floor (also available as a Matt / Flat finish).

GLOBE
1) (especially TV and Film) Jargon for a replacement lamp.
2) The glass part of a lamp.
3) The Globe Theatre in London.
See also BUBBLE, LAMP.

GLOVES
Used when lifting heavier lanterns or other equipment.

GLOW TAPE
Luminous yellow self-adhesive tape used to mark floors so that positions can be found in blackouts. A staple is often used to secure the tape to a floor where it might move.

GLS
General Lighting Service. Lamps designed for general everyday use.

GO
The action word used by stage managers to cue other technical departments. The word GO shouldn't be spoken by others on headsets (especially when the crew is on STANDBY) as they may assume it's the stage manager speaking.

GO UP
The time the show starts (e.g. 'What time does the show go up this afternoon?') This relates to the curtain going up at the start of the show (even if the theatre doesn't have a curtain). See also COME DOWN, LIGHTS UP.

GOBO
A thin metal plate etched to produce a design which can then be projected by a profile spotlight. There are hundreds of gobo designs available - common examples are breakup (foliage), windows and scenic (neon signs, city scapes etc.). The image can be used soft focus to add texture, rather than a defined image. A number of composite gobos in different COLORed lanterns can, with careful focusing, produce a COLORed image (e.g. a stained glass window). Greater detail can be achieved using a glass gobo, which consists of a thin layer of aluminium etched onto glass.

Origin of the term 'gobo'
There are a few possible origins for the word GOBO but nothing definitive yet.
Although it's tempting to believe it's an acronym or abbreviation for 'Graphical Optical BlackOut' or 'Goes Before Objective lens' this is not true, as the term is also used in connection with sound recording (a microphone gobo blocks sound from adjacent sources) and also in the film industry, where it's a piece of equipment to block light from the lens or an area. .
It could be short for Go-Between, as the gobo goes between the lamp and the lens.
Material from 1967 uses the word 'MASK', and no mention is made of 'GOBO', so we can assume the word wasn't in widespread use then for stage lighting. In the US TV/Film industry, a Gobo is a piece of material used to mask or block light, placed in front of a lantern (also known as a SHADOW MASK) and a Cookie (short for Cucaloris(from the Greek kukaloris: the breaking up of light)) is the same as a UK Gobo. PATTERN and TEMPLATE can also refer to a gobo in some areas.
In the film industry, the word gobo can be used as a verb (e.g. 'We need to gobo off that light so the camera doesn't see it').
Gobos are available in a wide range of sizes, for use in different profile lanterns and other projectors (e.g. moving lights). 
A size - 100mm outside diameter / 75mm image diameter
B size - 86mm / 64.5mm
D size - 53mm outside diameter
M size - 66mm / 48mm
E size - 37.5mm / 28mm
Moving lights use a range of different gobo sizes, so check the manufacturers website. 
Lighting Effects

GOBO HOLDER
A metal plate designed to hold a gobo of a particular size in a lantern of a particular type.

GOBO ROTATOR
See EFFECTS.

GOD MIC
A PA system setup for a director to use in a large venue to talk to everyone on stage without shouting, during rehearsals and technical periods. Also used in some small or experimental spaces for tech crew to talk to actors or other crew, if no headset comms system or radios are available. 

GODS
Colloquial term for the Upper Circle of the auditorium.

GOFER
Colloquial name sometimes given to a junior member of the crew, who is given instructions to fetch and carry equipment / tools etc. (i.e. 'Go For a wrench')

GOING DARK
1) See DARK.
2) Warning to people on stage that the lights are about to be switched off. Normally said during lighting plotting sessions or technical rehearsals. Obviously should not be done if there is any risky work on stage, or if anyone is up a ladder / using power tools / working on platforms / rehearsing choreography etc.

GONDOLA
(Costume) An enclosed easily transportable costume rail with removable side which enables large shows to manage huge quantities of costumes, wigs etc easily.

GPC
(US only) Grounded Pin Connector. A 3 pin plug used to connect instruments to cables / lighting circuits.  Also known as Stage Pin Connector. 

GPO
(UK or AUSTRALIA) General Post Office. Refers to a particular type of toggle switch used for manual telephone exchanges which is reliable, silent and heavy duty, and is perfect for Stage Management Desks. But is no longer manufactured. 

GRAMS
Refers to a Gramophone, originally the only way of playing back sound effects from vinyl or shellac record discs. A Grams cue, then, is a cue to play back recorded sound. Some TV productions (particularly shows that are shot "as live" or broadcast live) list GRAMS OPERATOR in the credits. The term is rarely used in theatre nowadays.

GRAND CIRCLE
See CIRCLE.

GRAND CURTAIN
(US) The main house tabs in a venue. Normally a variation of blue or red in COLOR, although a more neutral grey is often better for scenes played in front of it, or for taking colors and gobos as tab warmers.

GRAND DRAPE
See GRAND CURTAIN.

GRAND GUIGNOL
Shock theatre form originally from Le Grand Guignol theatre in Montmartre, Paris (opened in 1897). Specialised in portraying the macabre & gruesome to the delight and horror of the audience.

GRAND MASTER
See MASTER.

GRANDSTANDING
An actor who seeks applause and attention from the audience, regardless of how the character is supposed to behave. Also used in politics for a politician who says whatever a particular audience wants to hear, to get more applause and support from them. 

GRAPEVINE
The theatre community is very close, and news/rumours often spread via unofficial routes. This so-called GRAPEVINE means that people are often well-informed about latest news. It is also very important to make a good impression on everyone you meet in the business, as bad impressions will be spread around the grapevine very quickly. Modern tools such as Twitter have made the grapevine even more widely spread, and great care must be taken to not publish anything on Twitter that you wouldn't say to someones face. 

GRAPHIC
Short for GRAPHIC EQUALISER.

GRAPHIC EQUALISER
See EQUALISATION.

GREASEPAINT
Name refers to make up supplied in stick form, for application to the face or body. Needs special removing cream.

GREEN
(obsolete term) The part of the stage visible to the audience.

GREEN BAIZE
Prior to 17th century actors dying on stage, a green baize cloth was laid down on the stage to save their costumes from needing cleaning. This was also a useful anticipation builder for the audience, especially if the cloth was laid during the interval halfway into the performance. 
See also GREEN ROOM.

GREEN ROOM
Room close to the stage (i.e. the green) for the actors to meet and relax before or after going on stage. See the link below for some possible derivations of the term.
More about Green Room

GRELCO
(UK) A 2 way 5A or 15A electrical splitter, originally manufactured in the UK by Grafton Electric Company (hence the name Gr el co). Another name is SNAPPER (brand name) or in the US "TWOFER". Sometimes shortened to GRELLY. A three way splitter is known as a TRELCO, TRELLY (or THREEFER in the US). These splitters are always wired parallel (voltage equal, current shared).
See SERIES SPLITTER which enables (for example) two 115V lamps to be connected to a 230V supply.
[updated courtesy John Creed, 2017]
Museum of Old Electrical Items - Grelco

GRID / GRIDIRON
1) The support structure close to the top of the fly tower on which the pulleys of the flying system are supported. Constructed from metal or wooden beams. (Italian: gratticia / graticciata / graticcio)
2) Arrangement of scaffolding from which lanterns are hung in a performance space with no flying facilities. Grid is short for GRIDIRON.

GRIDDED
Any flying piece raised as high as possible into the flys, i.e.to the limit of travel of the flying lines, is said to have been gridded.

GRIP
(US) Member of stage crew responsible for moving items of scenery during the show. Usually wears black. A group of grips is a GRIP CREW. This term is borrowed from the film/tv industry, where a grip handles and sets up camera equipment and lighting.

GRIPPLE
Proprietary device designed originally for agricultural use that can be used to form eye terminations in wire rope for non lifting applications.
Submitted by Chris Higgs

HAAS EFFECT
A psychoacoustic phenomenon whereby an audience will focus on an actual sound source if the reinforced sound from speakers arrives 10 - 15 milliseconds later. The setting up of delays can be time-consuming but the Haas Effect can make a vast difference to the perceived quality of the sound in a show. The delays are set up by experimentation rather than by using distance/speed/time formulae.

HALF
1) The Half is a call given to the actors half an hour before they will be called to the stage for the beginning of a performance. It is given 35 minutes before the advertised time of commencement (in the UK). On Broadway, the Half is given 30 minutes before the start time.
Subsequent calls given are the 'quarter' at 20 minutes (UK), 'the five' at 10 minutes (UK) and 'beginners to the stage' at 5 minutes before curtain up (UK). See also FRONT OF HOUSE CALLS, QUARTER.
Also known as Final Call.
2) Lighting - half of full intensity, or 50%. 
See Calls and Cans

HALF K
A 500W lantern (usually Fresnel or PC) - K refers to Kilowatt (1000 Watts).

HALOGEN CYCLE
Chemical process occurring in Tungsten Halogen lamps which makes them possible. During the lamps life, Tungsten evaporates from the filament, and would normally deposit itself on the glass wall of a Tungsten lamp, causing it to blacken, and causing the output of the lamp to reduce until it finally blew. In a Tungsten Halogen lamp, the Tungsten combines with the Halogen gas elements present in the lamp envelope and is re-deposited back onto the filament. This process needs a very high temperature to operate, so Tungsten Halogen lamps are able to be a lot smaller, and run a lot hotter, than their Tungsten equivalents. See also Tungsten Halogen.

HAM
Exaggerated over-acting.

HAMARTIA
From Ancient Greek. In connection with Greek Tragedy, Hamartia is often defined as the hero's fatal flaw.
Wikipedia entry

HAND
(US) Short for Stage Hand (member of Stage Crew).

HANG / HANGING SESSION
The 'hang' is the American equivalent of the lighting rigging session in the UK - the time when the lighting equipment is rigged.

HANGING AN ACTOR
A difficult effect to pull off successfully on stage, and must absolutely not be attempted without professional supervision, for obvious reasons. 
Harnesses can be obtained which are designed for this effect, but standard safety harnesses are not suitable. The rope must have a safety-rated rope built into it, which is suitable for suspending the shock load of the actors' weight, which must be attached to the harness in such a way that it's not possible for the fake noose to ever tighten around the actors' neck. The hanging must take place with other members of the company present, who have been trained in how the system works under professional supervision. 
Simply using a rope with a weak point (e.g. using weak cotton to connect the noose to the rest of the suspending rope) is no longer recommended as there are situations where it may not break, and any chance of this will not be acceptable to a risk assessment process. 
A far safer way to hang an actor is to do it offstage, or use a blackout or blinding light along with a sound effect to misdirect the audience into thinking they've just seen a hanging. 

HANGING IRON
Ironmongery fitting fixed at the bottom of the back of a flown flat to which the suspension wire is secured.

HAPPY TRAILS
(US) Good wishes given to a member of cast leaving a long-running show, or to an entire cast when a show is closing.
The phrase comes from the 1950s Roy Rogers television show, where it was the title of the closing theme song:
"Happy Trails to you!
Until we meet again
Happy Trails to you
Keep smiling until then
Happy Trails to you
Till we meet again!"
The song was written by Dale Evans (the wife of Roy Rogers, and his co-star in the TV series).
Roy Rogers TV show closing credits (Youtube)

HARD POWER
A non-dimmed power supply to a lighting rig (or part of a rig). 

HARDBOARD
An engineered wood product made from highly-compressed wood fibres. It's cheap and hard-wearing. Oil-tempered hardboard is more resistant to wear and tear and is more waterproof, and is used as a stage floor surface. One brand name in the US is Masonite. 
Wikipedia entry

HARMONICS
High notes that are achieved on instruments of the musical instrument families when the performer lightly places his finger exactly in the middle of the vibrating string.The harmonictones produced by a vibration that go to make up the aural spectrum of any particular note, or grouping of notes.

HARMONY
(Trade Name) Range of 1000W lanterns produced by Rank Strand (now Strand Lighting) in the UK.
Strand Lighting website
Strand Archive

HARTING
Family-owned and run technology company, founded in 1945 and headquartered in Germany. 
The brand is known in technical theatre for their heavy-duty multipin connectors used as 'Lectriflex'. 
Harting Website

HAZER
See SMOKE MACHINE.

HD-TV
Widescreen (16:9) high-resolution digital TV format.
HD-TV basics website

HDBaseT
HDBaseT is a standard for connection and transmission of high-definition video, audio and control / data signals using a Cat6 cable. The standard was launched in 2010, and can transmit up to 100m using good quality cable. 
HDBaseT website

HDMI
High Definition Multimedia Interface. HDMI is a proprietary audio/video interface for transferring uncompressed digital video data and compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controller, to a compatible computer monitor, video projector, digital television, or digital audio device. 
Wikipedia entry

HEAD
See RADIO MIC.

HEAD CARPENTER
The head of the carpentry team that builds the wooden portions of the set.The team are sometimes known as the 'Carps'.

HEAD ELECTRICAN
US equivalent of the UK CHIEF ELECTRICIAN

HEAD FLY
The head of the fly crew who are responsibly for lifting scenery or other objects above the stage.

HEAD SOUND
The head of the sound department, which deals with any recorded music, sound effects, vocal reinforcement and music amplification required in the production.
See also NO.1 SOUND.

HEADS
The top lantern on a lighting boom. See SHINS and MIDS.

HEADS ON STAGE
A shouted warning (often just 'Heads!') for staff to be aware of activity above them. Also used when an object is being dropped from above.

HEADSET
1) General term for theatre communication equipment.
2) A headphone and microphone combination used in such communications systems with a beltpack.
See also CANS.

HEADSHOT
A photograph of an actor, distributed to agents, directors or casting directors. Headshots are not the same as portrait photos, and are designed to show the actors' face clearly in even lighting. 

HEALTH AND SAFETY / OHS / WORK HEALTH AND SAFETY
UK and AUS term to cover a range of legislation and guidance on how to work safely, and to reduce accidents or incidents. 
The legal component is the Health and Safety at Work Act (1974), but there are a number of regulations which relate to safe working. 
See COSHH, SAFE SYSTEM OF WORK, LOLER, PPE, PUWER, RIDDOR.
Safety in Live Entertainment on Theatrecrafts.com

IAMBIC PENTAMETER
(from Greek - having five 'iambs') A commonly used metrical line in traditional verse or verse drama. The term describes the particular rhythm that the words establish in that line, which can be described as a 'tick tock' rhythm. The rhythm is measured in small groups of syllables; these small groups of syllables are called "feet". The word "iambic" describes the type of foot that is used (in English, an unstressed syllable followed by a stressed syllable). The word "pentameter" indicates that a line has five of these "feet."

IATSE / I.A.T.S.E.
International Alliance of Theatrical Stage Employees (USA) Stage employees union.
IATSE website

ICOPER
Acronym for International Code of Practice for Entertainment Rigging.
A new standard, published in 2017. 
Download ICOPER at PLASA

IEC / I.E.C.
International Electrotechnical Commission. The UK mains inlet connector / 'kettle lead' is known as an IEC LEAD.
IEC website

IEM / I.E.M.
See IN EAR MONITORS

IFCB
Acronym for the four palettes used to control moving lights. Intensity (brightness of the beam), Focus (position of the beam), COLOR, Beam (focus quality of the beam - hard-edged, soft-edged, or split through a prism).

IFR (Inherently Flame-Retardant)
A description of cloth which is inherently flame-retardant and will remain so for the life of the cloth. The flame retardant qualities are a feature of the material, not a treatment applied afterwards. See manufacturer for full details. See also NDFR and DFR.

IGBT
Acronym for Insulated-Gate Bipolar Transistor. Electronic component used in later generation lighting dimmers. 
Wikipedia entry

ILDA
International Laser Display Association
ILDA website

IMAG
Short for Image Magnification - the use of live feed video cameras and huge video screens to bring the details of an artists' performance to a huge stadium-sized audience. 

IMPEDANCE
A term for the electrical resistance found in a/c circuits. Affects the ability of a cable to transmit low level (e.g. sound) signals over a long distance. Measured in Ohms. Speakers are rated according to power handling capabilities (Watts, W) and impedance (Ohms).

IMPRESSARIO
1) Now more likely to be called a Producer, the Impresario organised and financed the performing arts. Term originated in the Italian opera, in the mid 18th Century.
2) Automation control console and system by AVW Controls in London, UK. 
AVW Controls website

IMPROVISATION
A comment or behaviour by an actor or group of actors that is not rehearsed or prepared (or, sometimes, authorised by the director). If the improvisation helps the performance move forward, appropriately, due to a technical or other issue, then improvisation can be helpful. If, however, it's put in to raise a laugh or breaks character or the mood of the scene, it is frowned on. 
See also AD LIB. 

IMPULSE RESPONSE
(Sound) Abbreviated to IR. An Impulse Response is a digital recording of a burst of a full range of frequencies (known as an impulse) across the audible spectrum, which is used to create a digital 'acoustic autograph' of a space. The impuise response recording is analysed by software which can then be used to recreate the acoustic of the original space digitally.
This enables a precise match to how a recording sounded in the space when trying to recreate it in the studio. 

IN
(Flying) To fly a piece of scenery / lighting bar down towards the stage from the flies. The opposite is OUT. 

IN EAR MONITORS
Small headphones worn inside the ear by members of a pop band so they can hear the monitor mix (or the backing track they're miming to) without having lots of monitor speakers onstage. The advent of in-ear monitoring has improved the sound quality of the monitoring for these band members as they no longer have to try to hear the monitors over screaming from the audience. Each member of the group can have their own monitor mix which is guaranteed to be the same in every venue on the tour. Known as I.E.M.s or IEMs for short.

IN IS DOWN, DOWN IS FRONT
First line of a poem called Theatrical Logic, designed to highlight the complexity of technical theatre jargon!
Theatrical Logic

IN THE CAN
(Film Industry) A scene or sequence has finished being filmed. (e.g. "Thanks everybody - that scene is in the can now"). Refers to a roll of film being taken out of a movie camera and put into a metal film can to be taken for processing.

IN THE ROUND
Theatre in the Round is a form of audience seating layout where the acting area is surrounded on all sides by seating. There are often a number of entrances through the seating. Special consideration needs to be given to onstage furniture and scenery as audience sightlines can easily be blocked.
Stage managers and directors often use the idea of a clock face to describe actor positions on stage (e.g. the aisle nearest the technical point is described as the 12 O'clock position, with other aisles described as 3, 6 and 9 O'clock.)
See also ARENA, THRUST, END ON, TRAVERSE.

INCANDESCENT
Light source consisting of a metal filament (Tungsten) which glows white hot when current is passed through. See also Discharge Lamp.
How do Incandescent Light Bulbs Work?

INCIDENTAL MUSIC
Music heard by the audience in a non-musical performance, either as background atmosphere as underscore, or between scenes or to set the mood. Incidental music is not heard by the characters in the play, so is non-diegetic.

INDEPENDENT
1) An electrical power supply that is totally separate from the stage lighting control. Used for testing lanterns prior to connection to the lighting system and also for powering non-lighting equipment on stage and working lights. See NON DIM. 
2) A channel within the stage lighting control which has been temporarily switched to become independent from the rest of the channels which remain under the control of the operator.

INDUCTION LOOP
System which amplifies audio frequency currents (from a microphone over the stage) around a large loop of cable (around the auditorium) to generate a magnetic field which can be picked up by a hearing aid switched to the 'T' position.

INDUSTRIAL
Also known as a CORPORATE. An event or performance staged by a manufacturer or company in order to launch a product or celebrate a milestone of some kind. Such events are often spectacular. 

INFRA-RED
Invisible part of the electromagnetic spectrum with a longer wavelength than visible light. Infra-red remote controls are used for lighting desks and practicals. An infra-red-sensitive CCTV camera can pick up body heat activity even in a 'blackout'.

INFRASOUND
Very low frequency sound which is not normally audible by the human ear. Usually describes sound waves below 20Hz. At high enough volumes (sound pressure levels) sound waves as low as 12 Hz can be perceived by some ears. When they can't be perceived as sound, the waves can be felt as pressure either in the ear drums, or elsewhere on the body. Some scientists have linked the presence of infrasound in buildings (produced by air conditioning systems or large empty rooms) with feelings of unease, nervousness, or even perceptions of supernatural presences by visitors. 

INGENUE
The ingénue is a stock character in literature, film, and a role type in the theatre; generally a girl or a young woman who is endearingly innocent and wholesome. Ingénue may also refer to a new young actress or one typecast in such roles. 

INHIBIT
A way of taking control of a rogue lantern (or lanterns) at the lighting desk during the operation of a show and removing them from any further lighting states, until the inhibit is removed. Can also be used for removing the front of house lighting from a curtain call state. See also SUBMASTER.

INHIBITIVE SUBMASTER
See SUBMASTER.

INSERT
1) An additional route into a sound desk. 
2) An extra lighting state added into the sequence later. See POINT CUE.

JACK
1) Segmented audio connector. Mono Jacks have two connections - tip and sleeve, and are unbalanced. Stereo jacks have three connections - tip, ring and sleeve.
B-type jacks (also known as Bantam jacks) were originally designed for use in telephone exchanges and provide a high quality (and expensive) connection in jackfields.
A-type jacks are cheaper and more common, but more fragile. A type jacks are available in 2 sizes : quarter inch and eighth inch.
2) (US) A hinged brace. In the open position, it holds up a flat or other unit of scenery. A Tip Jack is a combinaton of a jack and castors so scenery can be supported or rolled. When it is in position, it is tipped to vertical. When rolling, it leans backwards.

JACKFIELD
An array of jack sockets ('jills'), providing connections to equipment/outlets etc. A patch panel.

JACKKNIFE STAGE
A type of set consisting of one or more wheeled rostra, which are fixed at one corner point, enabling the platform to pivot to reveal a different set / scene or to appear on stage or move offstage. See also WAGON STAGE, REVOLVE.

JAFIE
(Colloquial) Term of affection used by stage crew and sound folk, making disparaging comments about the Electrics (Lighting) team. 'Just Another F****** Ignorant Electrician'. Rarely used nowadays. 

JARDIN
French for Garden. See STAGE RIGHT.
More about Cour / Jardin

JONES PLUG / JONES SOCKET
Type of multipin connector used on some lighting desks for analogue outputs.
CINCH website

JONES, INIGO
Inigo Jones (July 15, 1573 - June 21, 1652) is the first significant British architect of the modern period, and the first to bring Italianate Renaissance architecture to England. He left his mark on London by single buildings, such as the Banqueting House, Whitehall, and in area design for Covent Garden square which became a model for future developments in the West End. He also made major contributions to stage design by his work as theatrical designer for several dozen masques, most by royal command and many in collaboration with Ben Jonson.
He is credited with introducing movable scenery and the proscenium arch to English theatre. 

JOSEF SVOBODA
Czech scenographer (1920 - 2002)
Josef Svoboda in the Backstage Heritage Collection Archive

JUKEBOX MUSICAL
A stage musical show that has been constructed from pre-released existing songs, usually from one artist or genre. Examples are The Buddy Holly Story, Mamma Mia and We Will Rock You.

JULIET BALCONY
A high level platform in a theatre or on a stage set that would work for the balcony scene in Romeo and Juliet. 

JUMPER
An adaptor from one type of electrical connector to another. For example, a 13 - 15A jumper has a 13A plug and a 15A socket at either end of a short cable. Also applicable to sound cables.

JUVENILE LEAD
The most significant role in a play or film that is performed by a young actor / actress. 

JUVES
Short for 'Juveniles' - child members of the company.

K
Lighting Industry Forum code which identifies the (original) recommended usage of different lamp types. K coded lamps are for use in general purpose flood lighting, and have a COLOR temperature of 2850°K. See also CP, A1, T, P2.

K1 HAZER
The Jem K1 Hazer is a high-performance hazer produced by Martin. It provides the combination of continuous operation, long hang time, and low fluid consumption for greater economy.
Martin Website

KABUKI
Traditional Japanese dance-drama. 
Japan Guide to Kabuki

KABUKI DROP
Method for dropping a cloth from a flying bar. It consists of a bar which attaches to a standard flying bar, and is able to spin around. The bar has prongs welded to it on which the drop is hung (drop has grommetted holes in the top which hook onto the prongs). Normally these prongs are above horizontal, so the drop stays hung. On cue, the pole is rotated so that the prongs point downwards, and the drop consequently falls.

KADER CLAMP
Metal clamp designed to fit onto the kader grooved roof beams of a clear span marquee. Typically, the clamps are rated with a safe working load around 150kg each, but the marquee supplier must provide you with information about what the roof beams are rated to support. Extra care should be taken if there are unusual loads on the roof (rain / snow / wind). 

KELVIN
See COLOR TEMPERATURE.

KENSINGTON GORE
A brand of fake blood used on stage and in movies, named after a London street. It was manufactured by a retired British pharmacist, John Tynegate, during the 1960s and 1970s, in the village of Abbotsbury, Dorset. Many varieties of blood, having various degrees of viscosity, shades and textures were available. Since Tynegate's death, the name "Kensington Gore" has become a generic term for stage blood. Kensington Gore was used in the film The Shining. Director Stanley Kubrick had several thousand gallons of it gushing out of an opening elevator during the elevator door scene.

KERF
The total width of the incision in a piece of wood or metal (etc.) made by a saw blade. 

KEY LIGHT
(Esp. TV & Film lighting) The dominant light source/direction in a naturalistic lighting state. In a sunny drawing room, the key light would be through the window, for a naturalistic exterior scene the direction of the key light could change as the sun progressed across the sky. See FILL LIGHT.

KEYSTONE
A function available on data projectors which allows the selective stretching of the horizontal component of the projected image so that it appears to be rectangular when projected from an angle above or below the projection surface. More advanced (expensive) projectors can also keystone the vertical component of the image, and some recent projectors can automatically detect the projection surface and can automatically keystone the image to fit. 
Before data projectors, special lenses were available for slide or film projectors to apply the keystone effect. 
The term comes from the wedge-shape of the stone placed at the top of an arch to spread the load of the wall above equally down both sides of the arch. 

KICKER LIGHT
Lanterns placed to the side of the actor to maximise the sculptural quality of the light are sometimes known as KICKERS.

KILL
To switch off (a light/sound effect); to strike/remove (a prop).
(e.g. Kill channel 6 please)

KILOWATT
1 kilowatt (1kW) is equal to 1000 Watts. The WATT is a measure of electrical power. The single letter 'k' is often used to represent 'kilowatt'. "2k fixture" means a 2000 Watt (or 2kW) lantern etc.

KIRBY WIRE
Wire used to fly an actor.
Named after George Kirby, who devised the first pendulum artiste flying system (in 1898). His company Kirby's Flying Ballet is still supplying flying equipment now.
See also FLYING HARNESS.
Kirby Flying - History page

KIT
1) General name for equipment, especially nice shiny equipment, leading to the comment 'That's a nice bit of kit' 
2) Short for Drum kit.

KK WHEEL
A type of animation disk which fits into the COLOR runners at the front of a lantern which rotates and breaks up the light beam to make it appear to be moving. Best used on a profile lantern containing a gobo. A KK Wheel is known in the US as LOBSTERSCOPE.

KLEIN BAG
A canvas tool bucket originally designed for 'utility' contractors in the US, stout canvas with a rope handle and plastic or leather base. Ideally suited to and adopted for collecting hoist chain. Available as strong and large enough for up to 30m lengths of 7mm / 5/16' hoist chain.
Submitted by Chris Higgs

KLEIN TOOL
Klein Tools Inc. have been making tools since 1857, the 'tool' referred to is a generic term for two items, the 'Chicago' or 'Haven' grip, which are self gripping wire rope pulling tools, useful for tensioning catenary wires and general wire rope gripping jobs in rigging.
Submitted by Chris Higgs

KLIEG LIGHT
Named after brothers John and Anton Kliegl, the Klieg Light was originally an intense carbon arc lamp especially used in filmmaking. Modern Klieg lights use Tungsten Halogen lamps. Klieg lights are either fitted with a fresnel lens and spherical reflector (for a wash of light) or a single or pair of plank-convex lenses and an ellipsoidal reflector for a spot light.

KNAP
(Stage Combat) The technique to create the sound of a hit when engaging in a stage fight scene where no hit took place. 

KOTHURNOS
(Greek) High shoes worn by tragic actors to increase their stature.

KVA
Kilo-Volt Amps. Unit of electrical power.

LADDER
1) Climbable piece of access equipment to reach a working platform or for short light-duty work at height. See ZARGES.
2) Non-climbable structure in the shape of a ladder from which lanterns can be hung in a vertical 'stack'.

LADY AND THE TRAMP
A Lady and the Tramp moment occurs when two people clearing and coiling LX or sound cables end up both coiling the same one. Named after the Disney classic animation where two dogs end up eating the same piece of spaghetti.

LAMP
A light bulb is used in domestic situations (i.e. in the home). In the industry, we only use LAMPS. As the saying goes, 'Bulbs is what you put in the ground'.
Example usage: 'The lamp in the DSC fresnel has blown'. In the TV/Film world, a lamp is called a BUBBLE or GLOBE.

LAMP ROUND
Periodic inspection of all light fittings around the theatre, to replace dead lamps / bulbs. Usually takes place before opening night.

LAMP TRAY
Lower section of the body of a theatre lantern on which the lamp holder is mounted. Some lamp trays are hinged, some are removable from the rest of the body. Modern safety legislation (UK) requires that the lamp tray cannot be opened until power is disconnected.

LAMPY
(colloquial term) Theatre / Rock & Roll lighting technician. Distinct from a 'Techie' who may also be a carpenter or stage crew member. A lampy only concerns him/herself with lighting.
A more generic electrician might also be called a Sparky, or Sparks.
See also JAFIE, TECHIE and NOISE BOY.

LANTERN
1) General term for unit of lighting equipment including spotlight, flood etc. Term now being replaced by the internationally recognised "luminaire" (esp. Europe) or "instrument" in the US.
See also FIXTURE.
2) Glazed section of roof usually in haystack form over the fly tower that automatically opens in the case of fire. An updraught is created which inhibits fire from spreading quickly into the auditorium, and prevents build-up of smoke at stage level.

LASER
Acronym of Light Amplification by Stimulated Emission of Radiation. A very high energy beam of light that remains virtually parallel throughout its length. Visible in the air only when a haze of smoke or dust is introduced. Great care is required when using lasers as this energy can cause permanent damage to the retina of the eye.
How Lasers Work

LATENCY
In digital live sound systems there are tiny time delays due to the processing time required to convert sound from analogue to digital and back again. This time period is known as the LATENCY of the system. 

LATEST TAKES PRECEDENCE (aka LTP)*
Abbreviated to LTP, this is a standard by which some lighting desks operate.
If there is more than one control on the desk affecting a particular channel, then the latest control to operate will be the one to affect the output on stage.
This system is used on desks with moving light functionality
See also HIGHEST TAKES PRECEDENCE.

LAUAN (US) / LUAN (US)
A three layer plywood made from coarse grained tropical woods. Suitable for backing, filler or light duty bracing; not suitable for structural uses or where a smooth paintable finish is desired. Also known as Phillipine Mahogany.

LAVALIER MICROPHONE
Originally, a mic worn around the neck on a string. Now applies to a small 'tieclip' microphone. These microphones are used for TV and also in musical productions requiring the amplification to be 'invisible'. The mic is worn in clothing, in hair / wigs, over the ear or on the face (heavily made-up).

LAY
The direction and angle in which strands are 'twisted' in rope making) which in turn determines the 'hardness' of the lay (flexibility) in fibre ropes and the 'pitch' (frequency with which a strand appears when viewed along one side) of any rope.
Submitted by Chris Higgs

LBO
Acronym for Light Board Operator. Also known as the Board Operation (or Board Op). 

LCD / L.C.D.
Liquid Crystal Display. LCD displays are in use on electrical and electronic equipment across the world, and LCD technology is also used in video projectors.
See also TFT.
How LCDs work

LCL
Abbreviation for Light CENTER Length. This measurement (in mm) is the distance between the top of the lamp base and the optical CENTER of the filament. This measurement is critical as it ensures that for a particular lantern, the filament is at exactly the correct position for maximum light output and efficiency. Many different lamp types exist, but there are far fewer lamp-base types, meaning it's possible to insert the wrong lamp into a lantern very easily, resulting in poor output and efficiency.
See also MOL.

LD / L.D.
Lighting Designer.

LE MAITRE
(Manufacturer) UK based manufacturer of pyrotechnic devices (Pyroflash brand name), smoke machines and other theatre effects
Le Maitre website

LEADER TAPE
Non-magnetic plastic tape used to begin and end sound tapes and to separate cues on tape. Clear leader tape is used to activate the automatic stop on some playback machines. Leader tape is available in a variety of colors.

LECTRIFLEX
Multipin connector for carrying multiple lighting circuits down a multicore cable. See also SOCAPEX.

LED / L.E.D.
Light Emitting Diode. LED technology is becoming extremely useful in the areas of architectural lighting and video walls. LED light sources are becoming brighter and cheaper. They are extremely efficient, and give off very little heat, making them ideal for display or architectural work. LED video walls are in use all over the world - they are more efficient and lighter in weight than projection alternatives.
The LED Museum
How LEDs work

LEE
(Manufacturer) UK based manufacturer of lighting gels. See COLOR FILTER.
Lee Filters website

LEG
1) Each sling used as part of a multiple sling, e.g. a 'two leg sling' has two slings used as the 'legs' of the sling. A bridle 'leg' is therefore one half of a two 'leg' bridle, or one third of a three way bridle, etc.
2) See LEGS.
Submitted by Chris Higgs

LEGIT VOICE
Singing term - refers to a classically trained voice (see also BELT VOICE)

LEGITIMATE THEATRE (US term)
The term "legitimate theater" dates back to the Licensing Act of 1737, which restricted "serious" theatre performances to the two patent theatres licensed^[1] to perform "spoken drama" after the English Restoration in 1662. Other theatres were permitted to show comedy, pantomime or melodrama, but were ranked as "illegitimate theatre". For more information click here.

LEGS
Vertical drape set as masking piece at the side of an end-on acting area. Usually set up in pairs across the stage and used in conjunction with borders to frame the audiences view. Legs are hung from flying bars, and are usually fairly narrow in width (1.5m - 3m). 
One of many possible origins of the phrase 'Break a Leg', meaning to take an extra encore from the legs after a successful performance.
French: Pendrillon (also used for wider tabs, but not full-width stage curtains)
More information on Break A Leg

LEKO
A type of ellipsoidal profile spot (aka ellipsoidal reflector spotlight or ERS), much used in the USA. Originally designed in 1933 by Joseph Levy and Edward Kook, the founders of Century Lighting (later Strand). The word is a contraction of their names (Levy & Kook). Also known as LEKOLIGHT. 
Leko in the Backstage Heritage Collection archive

LEMO
A small metal multipin connector used for connecting radio microphone heads into the transmitter pack.

LENS
Optical glass with one or both sides curved, the purpose of which is to direct light by concentrating or dispersing light beams.

LEVEL
1) The setting of a light or sound control channel. On a lighting desk, levels range from 0% to 100% (also known as FULL). On a sound desk, the bottom of the fader is ∞ (infinity) and the top may be +20. The fader is designed to be operated at it's optimal position which is labelled 0dB. The decibel (dB) scale is a measure of sound intensity. 
2) A platform used to change the height of an actor. Interesting dynamics between different characters in the play can be explored using various levels. 

M.U. / MU
M.U. is short for Musicians Union (UK).
Musicians Union website

MAC
A range of professional moving lights made by Martin in Denmark.
Martin website

MACBETH
See Superstition.

MACRO
A shortcut that can be user-created on software-driven devices (e.g. lighting desks, sound desks) that carry out an often-repeated set of commands at a single button press. (e.g. 'I've created a macro to stop the effects on the downstage moving lights'). A macro is first 'learned' - when in learn mode, all button presses are memorised, and can then be stored as a numbered macro, or to a specific macro key. 

MADI
Acronym for Multichannel Digital Audio Interface, this is a standard way of sending digital audio signals over distances over 100m. Developed by AMS Neve, Mitsubishi, Solid State Logic and Sony, it is defined and monitored by the Audio Engineering Society. The standard is also known as AES10. MADI supports serial digital transmission over coaxial cable or fibre-optic lines of 28, 56, or 64 channels; and sampling rates of up to 96 kHz with resolution of up to 24 bits per channel. 

MAENADS
In Greek mythology, the maenads were the female followers of Dionysus (Bacchus in the Roman pantheon), the most significant members of the Thiasus, the god's retinue.

MAGIC IF
Stanislavskian technique which encourages actors to explore how they would feel and what would happen IF the situation in which the character they are portraying was to happen to them, or IF their personal circumstances were different.

MAGIC SHEET
See CHEAT SHEET.

MAHL-STICK
A short stick used by scenic painters to steady the hand by resting its padded end against the surface being painted.

MAINTAINED LIGHTING
See Secondary lighting.

MAKE-UP
Products applied to the face or body of an actor to change or enhance their appearance. See also GREASEPAINT. Colloquially known as SLAP. 
Make-Up Resources at Theatrecrafts.com

MAKING THE NUT
(Colloquial term) The 'nut' is a break-even point, after which the show can pay it's bills. It's calculated either show by show or for the length of the production (some costly shows don't make their 'nut' until well into the run). The origin of the term is believed to be 'to survive, a squirrel has to find at least a nut a day. For a person to survive, they must make at least $xx a day -this dollar figure is their 'nut'.'

MANTLE OF THE EXPERT
The mantle of the expert is a student-centered dramatic-inquiry-based approach to teaching and learning invented and developed by Professor Dorothy Heathcote at the University of Newcastle upon Tyne in the 1980s.
This approach inverts the typical teacher-to-student model of teaching by allowing the students to dictate their learning and educational process through creative drama. The students, rather than the teacher, are the main communicators in this process. (From Wikipedia) 
Wikipedia entry

MANUAL DESK
A lighting desk where the interface between operator and dimmer is a fader, rather than a computer. Many modern manual desks have some memory facilities built in, but there are still a large number of venues with solely manual systems.

MARIE TEMPEST HINGE
Door hinge that has been reinforced by a screw lever to keep the door from opening by itself on a raked stage. Named after the actress Dame Marie Tempest (1864 - 1942).

MARKETING DEPARTMENT
See PUBLIC RELATIONS.

MARKING OUT
Sticking tapes to the floor of the rehearsal space to indicate the groundplan of the scenery. Also for marking position of furniture etc. within a set. Always be aware that some tapes may damage or mark some wooden floor surfaces! (sometimes known as the markup). 

MAROON
An electrically detonated pyrotechnic device giving the effect of a loud explosion. Made from gunpowder encased in stout cardboard or string. Must be used within a metal bomb tank. Originally developed in the second half of the 19th century to simulate the sound of cannon, it was often used to call out the volunteer lifeboat crew in an emergency.

MARQUEE
(USA) A permanent canopy over the entrance of the theatre, where the name of the show (and sometimes the stars) are displayed. 

MASK
1) Form of theatre where actors faces are covered with masks. 
2) Early word for GOBO.

MASKING
Neutral material or designed scenery which defines the performance area and conceals the technical areas. (e.g. a masking flat is designed to block the audiences view of backstage).
German Masking consists of 3 sets of flats or drapes lining the edges of the performance space (ie the 2 sides at 90° to the proscenium arch, and the rear of the space masked parallel to the pros. opening.) This type of masking is sometimes known as "Up and Down Masking" as it runs up- and down-stage. This term seems to be rarely used now.
French: Pendrillonnage à l’allemande
Italian Masking consists of a set of legs and borders which are set up in a configuration similar to forced perspective. The downstage legs are furthest apart, and each set of legs moving upstage is moved onstage, with the upstage set narrowest. The exact distances involved vary according to the size of the space, and the acting area required. The same applies to the borders.
Italian: quintatura

MASKING FLAT
A piece of solid scenery used to prevent audiences seeing backstage (or unwanted) areas. See also BORDER, MASKING.

MASKING TAPE
Paper sticky tape used to mark out the boundary of a surface to be painted or sprayed.

MASTER
1) An overall control fader or lever on a lighting or sound control board. The Grand Master takes precedence over all other controls and allows the operator to fade out the entire output of the lighting desk.
On a lighting desk the PRESET MASTER allows the control of a section of the desk independently from the rest. 
See also SUBMASTER. 
2) An original (e.g. Master tape, master plan) which should be used only to make a copy from which to work. 
3) A Department Head (e.g. Master Carpenter, Master Electrician).

MASTER ELECTRICIAN
See CHIEF ELECTRICIAN.

MATINÉE / MATINEE
Afternoon performance of a show. (From the Latin for 'of the morning', but who does theatre in the morning?)

MATRIX OUTPUT
Set of outputs on a mixing desk which allows the user to preset a number of output configurations. eg on a 8 x 8 matrix, each of the 8 group outputs from the channels can be routed to any or all of the matrix outputs.

MAXIMUM OCCUPANCY
The number of people that can be in a given room at any time. This is determined by the fire department, or a fire officer, making use of local regulations about the amount of space required for each person, and by the number of fire exits (and the size of exit walkways) and the number of toilets etc available. 
Obviously, the number must not be exceeded, as if there is an incident or accident, the insurance cover for the event / building may not be valid. 

MAXXYZ
Moving Light console produced by Martin.
Martin website

MBI
Metal Halide discharge lamp. See also DISCHARGE LAMP.