Glossary – By Letter

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).

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.

A2
Assistant Sound Operator/Engineer (Audio 2)

AAC
Digital audio encoding format. The name stands for Advanced Audio Coding. The format provides slightly better audio quality than the MP3 format.
File extensions in use for AAC files include .m4a, .m4b, .m4p, .m4v, .m4r, .3gp, .mp4, .aac.
AAC is used on all Apple devices (including iTunes downloads), and was developed in 1997. Like MP3, it uses lossy compression, but provides an improvement in audio quality for the same file size. 

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.

ABBY SINGER SHOT
(Film-making) Named after legendary film production manager Abner Singer, this refers to the penultimate shot for the day. Mr Singer was very clear with his crew that there was one more shot to go after the next one, enabling them to start preparing to clear the set and strike equipment. Although the Abby Singer Shot now usually refers to the end of a shooting day, it can also refer to a given location, especially on a tight TV shooting schedule. 
Abby Singer Shot Meaning & History

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
(UK) 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. 

ACCESSORIES
Additional equipment that adds functionality to a larger piece of equipment but which are not necessarily stored with (or sold with) the equipment. 
Accessories for a Fresnel stage lantern are a colour frame and a barn door. The Fresnel cannot function without a lamp or a power cable, so these aren't usually seen as accessories. 

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
Stands for Architecture for Control Networks. 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

ACOUSTIC SHELL
(also known as BAND SHELL or CHORAL SHELL). A hard smooth curved surface which is designed to reflect the sound from the stage towards the audience. Some venues have shells which can be removed / repositioned or flown out of view to change the acoustics of the venue for different types of event. 

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

ACT NUMBER INDICATOR
An indicator board visible to the audience on the proscenium arch of a theatre used for variety performances which showed the Act Number so the audience could tell who was on stage (after referring to their printed programme). 
One type of board used replaceable numbers which were replaced by hand, another type used a paper scroll containing the numbers which was advanced either mechanically or electrically. The most popular type used an array of light bulbs which were illuminated in patterns to depict the numbers. 

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').
An Acting Area Rehearsal (also known as a Blocking Rehearsal) involves the actors running through their moves around the set, and less focus on the quality of the characterisation. 
(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

ACTIVE SPEAKER
A speaker that contains a built-in amplifier, which requires a power supply and audio input signal to operate. 
Also known as a POWERED SPEAKER.
See also PASSIVE SPEAKER.

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 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 COLOUR MIXING
See COLOUR 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, via a menu screen, via small rotary selectors where you can set each digit of the address, or via DIP switches where each switch represents a binary digit which combine to give the full address.
In larger systems, where more than 512 channels are required, each block of 512 addresses is called a Universe. By default, Universe 1 is used, so DMX address 120 on Universe 1 is known as 1/120. 
Some control desks permit the use of absolute addresses, where the first address of the 2nd Universe, normally called 2/001, is numbered 513.

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).

AFM
American Federation of Musicians. See MUSICIANS UNION. 
AFM Website

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.

AGENT
An agent is a representative and promoter for actors and writers. The agents are contacted by producers and casting directors, and the agents contact the artists who are suitable for the roles / jobs. 

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.

AGV
Automated Guided Vehicle. Industrial transport device used in factory environments, and also in dark rides and other theme park environments. The vehicle can either operate on a fixed path (which could be a wire embedded in the floor of the attraction which the vehicle can sense) or be free-ranging, when other mechanisms are used to feed back the exact position and orientation of the vehicle to a central control computer.

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

AIRBURST
Pyrotechnic effect which is designed to be suspended from an overhead rig (e.g. lighting bars / truss). Different size airbursts are designed to be triggered at different heights from the ground, so ensure that the manufacturers guidelines are followed. 
The airburst effect is a flash and burst of sparks. 
Airbursts - Le Maitre website

AISLE
A passage through seating.

ALAN SMITHEE
A fake name adopted by a film director who doesn't want their real name to be associated with the final result. 
See also GEORGE SPELVIN

ALCOVE
A semi-enclosed recess in the wall of the auditorium, sometimes for technical equipment, sometimes for a statue or other decorative element. 

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.

ALPD
Formerly the ALD (Association of Lighting Designers), the association was renamed in mid 2021 to the Association of Lighting Production and Design (UK)
ALPD Website

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 colour temperature) as it becomes dimmer. LED lights maintain the same colour 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 audio signal from a computer, 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.

ANAMORPHIC LENS
Photographic lens which captures a wide angle image, and squeezes it horizontally so it fits onto a standard piece of film. A similar lens is used in the cinema to re-stretch the image to fill a wide cinema screen. 

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. Ångström.
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. They are 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.

ANTE PROSCENIUM
Sometimes (incorrectly) called ANTI PROSCENIUM. From Latin - ANTE means in front of the proscenium. Refers to lighting bars or other equipment rigged in the theatre on the audience side of the proscenium arch. Often shortened to AP. 
Also known as FOH (front of house). 
See also 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.

ANTIQUARIANISM
A movement which insisted on historically-accurate scenery and props on stage. The more stylized sliding wing flats were replaced by more detailed box sets including architectural features, props and furniture appropriate to the time period in whcih the show was taking place. Antiquarianism moved into theatres in the late eighteenth century in Europe. 

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

APERTURE
(Film/Photo) The adjustable hole through which light passes between the lens and the photographic film or digital sensor in a camera. A wider aperture lets more light through, a narrow aperture lets less light through. The same function as the IRIS of the eye (known as the pupil). 

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.

ARC-LINE
(Trade Name) A coloured plastic tube containing a number of small strobe units which, when triggered, flash in sequence down the tube. Many tubes can be connected together.
Arc-Line in the Backstage Heritage Collection

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).

ARDUINO
Open Source electronic prototyping platform. Consists of a microcontroller on a circuit-board designed to easily interface with sensors or outputs in the real world. Useful for electronic or animated props, visual displays etc. Thousands of applications. 
Arduino website

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.
Known in the USA as a SEMI (short for Semi-Trailer, where a trailer box with a rear axle only is pulled by a tractor unit). 

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. They are also a member of the stage 'crew'.
The ASM is reponsible for setting props used during the show, as well as carrying out a pre-show check list to ensure all props are in the correct place and that all furniture used on stage is correctly placed for the start of the show. 
An ASM may also have a small acting role in some performances (they are then known as an Acting ASM).
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

ASTM
American Society for the Testing of Materials. Founded in 1898 and based in Pennsylvania. The ASTM arose out of efforts by Charles Dudley to standardise specifications for materials used across the construction of the Pennsylvania Railroad. 
ASTM Website

AT RISE
(US) Stage direction at the start of a play text which describes the stage appearance / layout when the curtain rises (which is where the term comes from), who is on stage, and what they're doing. 

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.

ATMOSPHERIC SOUND
Ambient or Atmospheric sound can be used to define a location or to help the audience to understand the world of the play better.
In live performance, it consists of subtle and carefully balanced audio effects which should not overshadow the performance, but set the scene. 
In film-making, atmospheric sound in a location (with no dialogue or other actor sounds) is recorded so that a consistent audio background is available, to make sound editing an easier process, to smooth-over edits. The recording of atmospheric sound is known as the 'wild track'.

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 colour-changing or moving light are known as the ATTRIBUTES.
All moving lights will have PAN and TILT, with many having COLOUR wheels, GOBO selection, gobo rotation etc. as additional attributes.
LEDs can operate in a number of modes, based on the number of colour sources they have, as well as whether certain parts of the beam can be separately controlled. A basic LED fixture might operate in 3 channel mode, with the 3 controllable parameters being RED, GREEN and BLUE. More complex fixtures might add AMBER and/or WHITE, and the latest LED fixtures may have LIME as well.

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

AUDIO
Another name for the Sound department. 

AUDIO DESCRIPTION
A service greatly appreciated by those with impaired vision, Audio Description involves a describer sitting at the rear of the auditorium (in the booth if there is room) providing a narration describing the action on stage. The skill is in not getting in the way of the on stage dialogue, sound effects or other audible movements on stage, but filling in where vision would help with the plot.
Making Theatre Accessible

AUDITION
Process where the director or casting director of a production asks actors / performers to show them what they can do. Sometimes very nerve-wracking, but auditions can be a fairly painless process if handled properly. Performers are often asked to memorise a monologue from a play they like to perform for the director. Books full of suggested monologues are available. You may be asked to do a 'Cold Reading' which tests your own response to a piece of text you've not prepared. Some audition processes have pages of text available outside the audition room for actors to familarise themselves with before the audition.

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

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 or actors around stages on productions with sufficient budget. See MOUSE, SPADE, DOG, KNIFE.
Scenic Automation on Theatrecrafts.com

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.
Analogue desk: Each input channel will have a path to the Aux buss, which will usually have a master level control, before the signal leaves the sound desk via the Auxiliary (Aux) output. A cable is then run to the outboard equipment (e.g. graphic equaliser, digital effects processor, recording device, monitor mixing desk). If the outboard equipment needs a path to return the audio to the main system after processing (e.g. Equaliser, effects processor), an Auxiliary Return is used to come back into the desk. There will be an Aux Return master level control and the option to send that signal to the main outputs or (on some desks) to sub-groups. 
Digital desk: Aux busses are used to provide additional routes around the console through the on-board effects processor or EQ unit. The resulting signal is Returned to the main outputs or groups. 

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.