Glossary of Technical Theatre Terms – Beginners

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

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 (!!).

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.').

AISLE
A passage through seating.

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).

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.

ASM
Assistant Stage Manager.

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

BACKSTAGE
The part of the stage and theatre which is out of the sight of the audience. The service areas of the theatre, behind, beside or underneath the stage. Also refers to the personnel who work in the technical departments that work to create the performance, alongside the actors and musicians. 
German: Hinterbühne

BALLET
1) A widespread, highly technical form of dance with its own vocabulary based on French terminology.
2) A dance performance containing the music and choreography of a ballet.
Wikipedia entry

BEGINNERS
A call given by Stage Management to bring those actors who appear in the first part of a play to the stage. e.g. "Act One Beginners to the stage, please". The actors are then called by name.
A similar call is given after the interval (e.g. "Act Two Beginners to the stage please").
The call is usually given 5 minutes before the advertised performance start time, but this may vary depending on how long the actors take to get into position.
See also HALF, QUARTER.
See Calls and Cans

BLACK BOX
A kind of flexible small studio theatre where the audience and actors are in the same room, surrounded by black tabs (curtains). Doesn't necessarily describe the audience layout, which can be easily reconfigured.The stage can be defined by a change of flooring (e.g. black dance floor), or a raised platform. If actors leave the stage, they do so through gaps in the curtains. 
A black box type of venue is easy to set up in non-theatre spaces, and can be found occupying hundreds of spaces around cities such as Edinburgh during their Fringe Festivals. 

BLACKOUT
1) Complete absence of stage lighting. Blue working lights backstage should remain on and are not usually under the control of the board, except during a Dead Blackout (DBO), when there is no onstage light. Exit signs and other emergency lighting must remain on at all times.
2) The act of turning off (or fading out) stage lighting (e.g. "This is where we go to blackout")
3) Blackout Check (or Dark Check) takes place in some multi-purpose venues to ensure that window curtains or blinds are closed and that there is no stray light either from adjacent rooms or the outside world, before the audience is admitted. 

BLACKS
1) Black clothing worn by stage management during productions.
2) Any black drapes or tabs, permanently or temporarily rigged. Used for masking offstage and technical areas.
Running Blacks are full stage width black tabs with a split half way, which are usually fitted to a tab track so that they can be opened and closed horizontally AND flown in and out. The tab track control can either be operated from stage level or from a fly floor (when they're flown out).
Hard Blacks are black-covered scenic flats used as masking. 
A Full Stage Black is a black cloth which can be flown in and is the full width of the stage. This is used to go upstage of a gauze to make transformation scenes work effectively, or can be used as a neutral backing for carefully lit scenes downstage.
Blacks flown vertically at the edge of the stage are known as LEGS.
Blacks across the top of the stage are BORDERS.

BLOCKING
The process of arranging moves to be made by the actors during the play, recorded by stage management in the prompt script. Positions at the start of scenes are noted, as are all movements around the stage (using terms such as 'Gardener X DSL' meaning the Gardener crosses to downstage left.) It must be described in minute detail, but simple enough to enable anyone to read and understand it. As well as being used to 'run the show' the prompt book is also used for the rehearsal of the understudies. 
Stages which are not end-on must often use alternative notation, sometimes based on the clock face or the points of a compass.
Blocking Notation

BOOK FLAT
Two flats hinged together on the vertical edge, to be free standing, and normally used as a backing for a doorway or window. They should always be 'run' with the hinged edge leading, to prevent them opening up. Book flats are free-standing when angled open, allowing quick setting and compact storage. Booking describes the action of opening or closing a book flat.
Flats - Types and Methods

BORDER
A narrow horizontal masking piece (flattage or cloth), normally of neutral colour (black) to mask the lighting rig and flown scenery from the audience, and to provide an upper limit to the scene. Often used in conjunction with LEGS.
In part of the 20th century, borders were made from asbestos materials, but are now made from fire-retardant cloth (e.g. Wool Serge). 
Spanish: Bambolina

BOX OFFICE
(UK) Part of the theatre front of house area where audience members can buy tickets. Most Box Offices are now computerised, and offer phone reservations. Some offer online (internet) bookings also. 
Also known as the Ticket Booth (USA). 
See also WILL CALL.

BOX SET
Naturalistic setting of a complete room built from flats with only the side nearest the audience (the fourth wall) missing.
A single static box set that represents more than one room is called a COMPOSITE SET (for example if the living room and the kitchen are both on stage permanently). 

BREAK A LEG
A superstitious and widely accepted alternative to 'Good Luck' (which is considered bad luck). More available at the link below.
More on Break A Leg

CALL
1) A notification of a working session (eg a Rehearsal Call, Band Call, Photo Call, Focus Call). A rehearsal call for the next day / week used to be posted on a Call Sheet on the stage door noticeboard, but is now often an online document, updated by the stage management team. A 'Company Call' means the full cast and crew are called for the rehearsal. 
2) The period of time to which the above call refers. (eg "Your call for tomorrow nights show is 6.55pm")
3) A request for an actor to come to the stage because an entrance is imminent (these are courtesy calls and should not be relied on by actors - eg "This is your call for the finale Mr Smith and Miss Jones")
4) An acknowledgement of applause (eg Curtain Call)
5) The DSM on the book is said to be "calling the cues".
6) The Colour Call is a list of lighting gel required for the lighting rig.
7) The Final Call is also known as The Half - 35 minutes before the performance starts, and the latest time when the cast and crew should be in the theatre.

CALLBACKS
Following an audition, the director may ask to see a shortlist of actors again - they are called back for an additional audition to enable the director to make her/his decision.

CAST
The members of the acting company. The Cast List contains the names of the actors and the characters they'll be playing. 
Dramatis Personae is a Latin term for a list of the characters in a play.

CASTING
The process of the director choosing actors to perform the characters in the play.

CENTRE CENTRE
(CENTER CENTER in the USA) - the position in the centre of the stage space. Downstage Centre (DSC) is the position at the front of the stage, Upstage Centre (USC), and Centre Stage (CS) or CENTRE CENTRE is the centre. House Centre / House Center is the centre line of the auditorium (which is usually the same as that of the stage).
Blocking Notation

CENTRE LINE
Imaginary line running down the stage through the exact centre of the proscenium opening. Marked as CL on stage plans. Normally marked on the stage floor and used as a reference when marking out or assembling a set. A chalked snap line can be used to mark the line in the rehearsal room and on stage.
Known in the US as CENTER LINE.
House Centre / House Center is the centre line of the auditorium (which is usually the same as that of the stage).
See also SETTING LINE.

CLEARANCE
Message passed to Stage Management from the Front of House Manager that the house is ready for the performance to begin. (ie everyone is in their correct seat and there are no coach parties coming through the doors). Announced as 'We have Front of House Clearance'.

COMPANY
The cast, crew and other staff associated with a show.

COSTUMES
Clothes worn by the actors onstage. The responsibility of the WARDROBE DEPARTMENT.

CUE
1) The command given to technical departments to carry out a particular operation. E.g. Lighting Cue, Fly Cue or Sound Cue. Normally given by stage management, but may be taken directly from the action (i.e. a Visual Cue).
Departments are often abbreviated: Lighting is LX, Sound is SD (or sometimes SX, but this is too similar to LX, so SD should be used). 
2) Any signal (spoken line, action or count) that indicates another action should follow (i.e. the actors' cue to enter is when the Maid says "I hear someone coming! Quick - Hide!" - this is known as a Cue Line. 
Cues given verbally may be known as 'audible cues', although as this is the normal type of cues, they're usually just called 'Cues'. Cues that technical operators take themselves, without an audible cue, are known as Visual Cues. 
3) A journal published between 1979 and 1988. A complete collection of CUE journals is available on the Backstage Heritage Collection website to read online.
The Prompt Book

CUE TO CUE
(also known as 'Topping and Tailing')
Cutting out action and dialogue between cues during a technical rehearsal, to save time. (e.g. "OK, can I stop you there - we'll now jump to the end of this scene. We'll pick it up from Simon's line "And from then on it was all downhill" in a moment. OK - we're all set - when you're ready please.")

CURTAIN CALL
At the end of a performance, the acknowledgement of applause by actors - the bows.
Hungarian: tapsrend.

CYCLORAMA
Usually shortened to just cyc (pronounced sike). The Cyclorama is a curved plain cloth or plastered wall filling the rear of the stage or TV studio. Often used as a sky backing to a traditional set, or as the main backing for a dance piece etc. The term is often loosely applied to a blue skycloth, or any flattage at the rear of the stage. Although strictly a cyc should be curved, most cycs are flat with curved wraparound ends. A more effective backing can be obtained by hanging a sharkstooth gauze just in front of the plain white cyc which gives a hazy effect of distance.
From Greek Cyclos (circle) and Horama (view or vision).
The first plaster cyclorama in the UK is believed to be at the Festival Theatre, Cambridge (1929)
See also BOUNCE, ISORA. The German equivalent term is operafolie.

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.

DIALOGUE
The spoken text of a play - conversations between characters is dialogue. See MONOLOGUE and DUOLOGUE.

DIRECTOR
There are many types of director.
Broadly, the role involves being responsible for the overall artistic vision of a production.
ARTISTIC DIRECTOR - Normally in charge of the programming of a venue. May also direct shows.
EXECUTIVE DIRECTOR - Manager in charge of the administration of a venue.
TECHNICAL DIRECTOR - In charge of the technical requirements of a production.
(The term LIGHTING DIRECTOR is used in the UK for a TV Lighting Designer).

DOOFER
An object or tool that you're not sure of the correct name for. For example, 'Pass me the doofer so I can sort this thingy'.

DOWNSTAGE
1) The part of the stage nearest to the audience. It's called Downstage because it's the lowest part of a raked stage. Downstage Left (DSL), Downstage Centre (DSC) and Downstage Right (DSR) are commonly used for the areas towards the front of the stage. [See Diagram]
2) A movement towards the audience (in a proscenium theatre).

DRAMATIC PAUSE
A brief pause (a few beats) in an actors' delivery of a line to emphasise a moment or to heighten anticipation. 
It's important that the DSM does not shout out the next line, while the lead actor is pausing dramatically. 

DRESS REHEARSAL
A full rehearsal, with all technical and creative elements brought together. The performance as it will be 'on the night'.
German: hauptprobe (final rehearsal)

DRESSING ROOMS
Rooms containing clothes rails and mirrors (often surrounded with lights) in which actors change into their costumes and apply make-up. Dressing Room doors have a list of the actors contained within.
See also GREEN ROOM.

FLAT
A lightweight timber frame covered with scenic canvas, or plywood. Flats are used to provide a lightweight and easy to move and re-configure backdrop to a stage set. Flats sometimes have windows or doors built into them to provide extra flexibility, for use in realistic settings. Masking flats are used to hide areas the designer does not want the audience to see, or to provide actors with an exit, or somewhere to store props.  
(UK) A flat is supported by a stage brace and brace weight, connected to the flat using a screw eye. 
Hardboard is sometimes used, but is unnecessarily heavy and will lose it's shape in time. Most theatres have a range of stock flattage made to a standard size, and re-used many times.
A Rail is a horizontal batten within a flat.
A Stile is a side or vertical piece within a flat.
A Sill is the bottom rail of a flat.
A soft flat is covered with canvas, and a hard flat is covered with plywood.
See also BOOK FLAT, HOLLYWOOD.
[French: Flat = panneau]
Flats - Types and Methods

FRONT OF HOUSE (FOH)
1) Every part of the theatre in front of the proscenium arch. Includes foyer areas open to the general public.
2) All lanterns which are on the audience side of the proscenium and are focussed towards the stage.
The backstage areas of the theatre are known as Rear of House (ROH).

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-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).

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

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. 
See also BEGINNERS.
2) Lighting - half of full intensity, or 50% (e.g. 'Can I have channel 12 at half?'). This dates from a time when lighting was manually controlled, and accurate percentage-point levels were not achievable (or at least, not repeatable accurately). Nowadays, designers are more likely to ask for 'channel 12 at 50%' and then 'up a point' or 'down a point', meaning +/- 10%.
See Calls and Cans

HOUSE
1) The audience (eg 'How big is the house tonight ?') The count of how many are in the audience is known as the House Count, and may be different from tickets sold, as some people may not attend. 
2) The auditorium (eg 'The house is now open, please do not cross the stage')

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

INTERVAL
Break between sections of a performance. During a play, the interval is normally half way through a standard length performance (approx 1 hour each half) and is usually 15 or 20 minutes in duration. Known in the US as an INTERMISSION.
For a full house, a 20 minute interval may be necessary. However, if there are no refreshments available, the interval can be shorter. 
A performance of less than 90 minutes in length could run straight through with no interval, although this wlil affect the theatres' takings for the night. 

LINES
Scripted words to be spoken by actors.
Example phrases: "Do you know your lines for Scene 2 yet?", "You missed a few lines at the end of the scene", "What's my next line".
See also SIDES.

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). 
The groundplan has lines on it, which correspond to easily-found locations in the theatre - most commonly, the centre line and the setting line (which is the proscenium line, or the edge of the stage).
Measurements on the plan can easily be scaled up to the real-life measurements, and the position can be marked on the stage floor by measuring from the real-world centre line and setting line in the theatre.

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

NODA
UK National Operatic and Dramatic Association, for amateur theatre producers, performers and crew.
NODA website

NON-VERBAL
Literally, anything involving communication or expression without words. PHYSICAL THEATRE and DANCE are examples of types of theatre which can be non-verbal. 

OFFSTAGE
1) A movement towards the nearest side of the stage from the centre. (e.g. 'Focus that spot offstage a bit please')
2) The area out of sight of the audience (e.g. 'Get that donkey offstage !')

OPEN
The start of the run of a show in a venue. (e.g. 'When does the new musical open at the Variety Theatre?' or 'The show opened a few weeks ago - it's had some great reviews'.)

PARODOS
Parodos (also parode and parodus, plural parodoi, Ancient Greek) is a term used in the theater of ancient Greece, referring either to a side-entrance, or to the first song sung by the chorus after its entrance from the side wings.

PLAY
A piece of text containing lines and stage directions designed to be performed live on a stage in front of an audience. 
A play rarely contains wordy prose descriptions of locations or scenarios, but sometimes the layout of a scene is described at the start of the scene to enable the production team and actors to see quickly what elements the stage set should consist of. The design of the stage (the layout, materials, finishes and colours used) is the job of the set designer. The director of the play works with the actors to bring the text to life, which may involve a large reworking of the original playwrights descriptions of the scene. A performing licence is required from the plays' publishers to give permission for the play to be performed, which will involve a payment for royalties to the playwright. This licence may also involve stipulations that the text must be performed exactly as written with no additions or omissions. 
A Teleplay is a script written or adapted for a television production.
A Screenplay is a script for a TV or Film production. 
See also MUSICAL, RADIO PLAY. 

PLAYWRIGHT
The author of a play. Also known as a dramatist.

PRESET
1) Anything in position before the beginning of a scene or act (eg Props placed on stage before the performance, lighting state on stage as the audience are entering.)
2) The process of putting any part of the production into its' starting position / setting. A Preset Checklist is used by stage management and all other technical teams, to ensure that everything is correctly set to start the show.  
3) An independently controllable section of a manual lighting board which allows the setting up of a lighting state before it is needed. Each preset has a master fader which selects the maximum level of dimmers controlled by that preset. A control desk with two presets is sometimes known as a '2 scene preset' desk. 

PRESHOW
The period before the performance begins, when the audience may be in the front-of-house areas, or even in the auditorium. 
The preset (pre show lighting state) is shown on stage, and can be used to set the mood for the performance. Preshow music or a soundscape is also used for the same reason. 

PROFESSIONAL
Normally used for someone who's regularly paid for a particular job (as opposed to an amateur, who does it for fun). A professional attitude is essential when working in the theatre - this means you have to behave as if you were being paid. The theatre world is a very small community - if you behave badly or upset someone, it's highly likely you'll meet them again, and they will remember you!

PROMPT CORNER
Area, traditionally on the stage left side of the stage, from which the stage manager (or DSM) controls ('prompts') the performance, from the prompt desk.

PROPS
(Properties) Furnishings, set dressings, and all items large and small which cannot be classified as scenery, electrics or wardrobe, and which actors interact with. Props directly handled by actors are known as HAND PROPS, props which are kept in an actors' costume are known as PERSONAL PROPS.

PROSCENIUM ARCH
The opening in the wall which stands between stage and auditorium in some theatres; the picture frame through which the audience sees the play. The "fourth wall". Often shortened to Proscenium or Pros Arch.
In some older theatres, the Proscenium Arch is ornate and painted to contrast with the surrounding walls, to really make it stand out. Nothing outside the Proscenium Arch was part of the show.
However, as there are many different audience layouts now, many theatres (particularly multi-purpose studio theatres) have no Proscenium Arch at all, or it may not be decorated as such.
See END ON.
Italian: Boccascena
French: cadre de scène

RADIO PLAY
A play that has been written specifically for an audio-only environment, usually to be broadcast on the radio. 
Radio Drama at Theatrecrafts.com

RAKED STAGE
A sloping stage which is raised at the back (upstage) end. Many theatres with a 'stalls' seating area used to be built with raked stages as a matter of course. Today, the stage is often left flat and the auditorium is lifted to stage level and above to improve the view of the stage from all seats. A rake is expressed as a ratio (eg a 1:25 rake rises by 1cm vertically over 25cm horizontally).
See also ANTI-RAKE.

RUN
1) A sequence of performances of the same production. (e.g. 'How long is the run of this show?' or 'This show runs for two weeks')
2) A rehearsal of the whole show or a section of it (e.g.'This afternoon's rehearsal will be a run of Act II followed by notes'). Run-throughs early in the rehearsal schedule are sometimes known as STAGGERS as actors are unsure of their lines.
A SPEED RUN is a rehearsal at faster than normal pace, concentrating on actor moves and entrances / exits rather than the quality of performance. This can only take place in the rehearsal room - once technical elements are included, a CUE TO CUE run is used, which jumps over long sequences with no technical elements to concentrate on polishing the cues. 
See also ITALIAN RUN, RUSSIAN RUN

SET
1) To prepare the stage for action. (verb) - e.g. 'Have you set the chairs for Act 1?'
2) The complete stage setting for a scene or act. (noun) - e.g.'What's the set for the finale?' French: décors.
See also RESET. 

SIDES
Printed pages of lines given to actors on a film or TV show. Lines are often changed / refined at the last minute, so a script printed at the start of the project will be out-of-date very quickly.
Sides are also given out at auditions for actors to work with, without needing to give them the whole script. 
See also LINES.

STAGE LEFT / RIGHT
Left/ Right as seen from the Actor's point of view on stage, when they are facing the auditorium. (ie Stage Left is the right side of the stage when looking from the auditorium.)
Stage Right = OP (Opposite Prompt) Abbreviated to SR. French: Cote Jardin, Netherlands: Toneel Links (translates to Stage Left!)
Stage Left = PS (Prompt Side) Abbreviated to SL. French: Cote Cour, Netherlands: Toneel Rechts (translates to Stage Right!).
NB: The Netherlands, Portugal and Germany use the opposite to the rest of Europe; i.e. Stage Left UK = Stage Right. The directions are seen from the director's and audience's perspective, NOT the actors. In Portugal Isquerda (left) is the equivalent of UK Stage Right and Direita (right) is the equivalent of UK Stage Left.

STAGE MANAGER PHRASES
"Get on your cues" - actors and crew members must concentrate so that they react as soon as they get a cue, not once they notice others reacting. 
"Quiet Backstage" - there should be no talking backstage or in the wings unless essential, and then only at a whisper. 
"Quiet On Cans" - the headset system (for communicating between crew members) must only be used for giving and receiving cues. There should be no unnecessary chatter.

STAPLER
Essential tool for attaching cloth to wooden frames / flats. 

STEEL TOE-CAPPED BOOTS
Essential footwear for crew members working in technical theatre. Sometimes known as Steelies.

TABS
1) Originally "tableaux curtains" which drew outwards and upwards, but now generally applied to any stage curtains including a vertically flying front curtain (house tabs) and especially a pair of horizontally moving curtains which overlap at the centre and move outwards from that centre.
If the tabs are flown, the instruction TABS IN is used to fly them in to cover the stage, and TABS OUT reveals the stage to the audience. If the tabs move horizontally, the tabs OPEN (to reveal the stage) and CLOSE (to cover it). 
[In French, tabs are Rideau. The main tabs or house tabs are Rideau d'avant-scène. In Spanish, the main tabs are Bambalinón.
A narrow stage curtain used for masking is Pendrillon
In Italian, tabs are Sipario.]
2) TABS was a journal published by Strand Electric between 1937 and 1986, about stage lighting and other equipment produced by the company. The Backstage Heritage Collection archive has a complete collection of TABS journals for you to read online.
TABS archive

TECH
1) Short for Technical Rehearsal. (e.g. 'The Tech took 14 hours')
2) A member of (amateur) crew ('I'm the lighting tech for this show')

TECHNICAL ELEMENTS
Technical elements stand alongside the text of the performance and help to reinforce themes and communicate ideas, and to ensure the audience understand and appreciate the story, and to help the actors tell the story. 
Commonly used technical elements include:
Scenery / Set: The physical environment in/on which the actors perform
Costume: Everything worn by the actors
Props: Small items placed on the set and/or carried by the actors
Lighting: Enables the audience to see the actors and physical elements, and adds additional atmosphere and  layers of meaning through use of colour and direction of light. 
Sound: Enables the audience to hear the actors and/or music, and also adds a layer of audio in addition to the text, to, again, reinforce meaning and add atmosphere. 
Wigs, Hair & Make-Up: Adds a layer of additional character to the actors' performance by altering their physical appearance to be more in-keeping with the period or character being portrayed. 

TECHNICAL REHEARSAL
(also known as the TECH RUN, or just TECH). Usually the first time the show is rehearsed in the venue, with lighting, scenery and sound. Costumes are sometimes used where they may cause technical problems (eg Quick changes). Often a very lengthy process. Often abbreviated to the Tech.
A DRY TECH is without actors to rehearse the integration of lighting, scenic changes etc. It follows that a WET TECH is a full technical rehearsal with actors and all technical elements, although this term isn't used as often as DRY TECH.
A PAPER TECH is a session without the set or actors when the technical and design team talk through the show ensuring everything's going to work as planned. Stage Managers can use this session to ensure all is written correctly in the Prompt Book.

THE TOP
The beginning of the performance. (e.g. 'Let's go back to the top to try the opening one more time'). 
See also TOP AND TAIL. 

THEATRE WORDS
OISTAT project to offer translations of theatrical terminology into global languages. 
Although an app was available, it doesn't work on latest versions of smartphones. 
See website for latest information.
Theatre Words website

TREADS
General name for any stage staircase or set of steps used on stage. The step of the staircase is called the tread, and the height of the staircase depends on the number of risers. The length of the staircase is called the going. Treads can be either open or closed string - meaning whether the riser is solid or not. The carriage provides the structural support for the treads, and can be either closed carriage or open carriage. Open carriage treads have nothing above / enclosing the top surface of each riser. Closed carriage treads may have a continuous structural piece enclosing the edges of the tread unit.

UPSTAGE
1) The part of the stage furthest from the audience. It's called Upstage because on a raked stage the stage slopes down towards the audience to improve sightlines. The furthest from the audience is literally higher due to the slope of the stage, so moving from close to the audience involves walking up the raked stage, towards 'Upstage'. 
US = Upstage, USC = Upstage Centre. USL = Upstage Left. USR = Upstage Right (see diagram)
See also DOWNSTAGE, ONSTAGE. 
2) When an actor moves upstage of another and causes the victim to turn away from the audience s/he is 'upstaging'. Also, an actor drawing attention to themselves away from the main action (by moving around, or over-reacting to onstage events) is upstaging.

VISUAL CUE
A cue taken by a technician from the action on stage rather than being cued by the stage manager. Often abbreviated to "Viz" or "Vis".

WINGS
1) The out of view areas to the sides of the acting area (known as FLÜGEL in German). The wings are best identified by their position on stage (e.g. "Clive exits through the downstage left wing") but they can be identified by number if there are too many exits, with the downstage wing starting as 1, with stage left and right added to identify the side (e.g. "Sarah exits 2L").
2) Scenery standing where the acting area joins these technical areas.