Theatre Terms

image of question markHere you'll find over 1000 definitions of theatrical terms, from Aside, Beam Angle, and Camlock, to Upstaging, VU Meter, and Wagon.  Fully searchable, our glossary is helpful for technical staff, directors, actors, producers, or anyone wanting to better understand the inner workings of theatre.

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Term Definition Cross Reference Link
IMPEDANCE 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. Speakers are rated according to power handling capabilities (Watts, W) and impedance (Ohms).
IMPRESARIO A producer, especially of musical entertainments.
IMPROV Improvisation
IMPROVISATION A spontaneous form of theatre that is inspired by the audience and so is never the same show twice. Suggestions such as places, opening lines of dialogue, television shows, emotions, etc. are supplied by the audience. Then the suggestions are stretched to the wildest depths of the imagination and explored by the players who use an arsenal of games and scenes of high caliber humor or drama -- all produced on the spot. Improvisation as defined by Viola Spolin.
IMPROVISE To improvise is to invent lines or business not in a script, to ad-lib. Improvisation
IN FOUR Said of a scene played in an acting area bounded on the upstage side by an imaginary line across the stage form the left wing farthest upstage to the right win furthest upstage, and on the downstage side by the "in three" area. In three
IN ONE Said of a scene played in an acting area bounded on the upstage side by an imaginary line across the stage from the left wing furthest downstage to the right wing farthest downstage. Also said of a curtain position at the same line; thus to play a scene "in one" usually means to play it on the downstage area in front of the curtain (usually while scenery is being changed behind the curtain.)
IN THE ROUND A stage setup in which the audience is seated completely around the playing area, as in an arena stage.
IN THREE Said of a scene played in an acting area bounded on the upstage side by an imaginary line drawn across the stage from the left wing to the right wing three-quarters of the way upstage.
INCANDESCENT Light source consisting of a metal filament (Tungsten) which glows white hot when current is passed through.
INDEPENDENT 1) An electrical power supply that is totally separate from the stage lighting control. Used for testing instruments prior to connection to the lighting system and also for powering non-lighting equipment on stage and working lights. 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.
INFLECTION The variation in the pitch of an actor's voice as he reveals emotion.
INFRARED 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.
INGENUE (French, pronounced on-ja-noo). The role of a sweet, naïve young woman; also an actress who plays young women's roles.
INSERT 1) An additional route into a sound desk. 2) An extra lighting state added into the sequence later. Point Cue
INSET A small scene set inside a larger one.
INSTRUMENT General term for unit of lighting equipment including spotlight, flood etc. "Instrument" is more common in the U.S., "Lamp" in U.K., but both terms are often replaced by the internationally recognized "luminaire".
INTELLIGENT LIGHT Another name for an automated lighting instrument in which certain functions such as panning, tilting, focusing, dimming, beam shaping and coloring, etc., are motorized and remotely operated from a control console.
INTERMISSION A period between acts, when the houselights are brought up, and the audience is encouraged to move into the lobby, outside, etc.
INTERPOLATION Dialogue, song, or stage business inserted into a script by a performer or director. Interpolation is illegal in copyrighted works without the permission of the author(s) or their representative (agent).
IRIS Adjustable aperture which, when placed in the gate of a profile instrument, varies the size of a beam of light. Originally, iris diaphragm.
IRISING Using the adjustable aperture on a lighting instrument to reduce the size of the light beam hitting the stage. If the aperture permits it, the size of the beam can be made quite small (referred to as "the button", or closed altogether.
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