Set
The scenery for a particular show or an individual scene.
Upstage
The back of the stage away from the audience.
Downstage
The front part of the stage towards the audience.
Wings
The area on either side of the stage, usually invisible to the audience, that the actors use before going on stage or where the props are kept ready to be brought on stage.
Cue
A signal for an actor to go on stage or undertake some audible activity off stage that is called for in the script.
Doubling
When an actor plays more than one part in a play.
Ghost
A singer used as a singing voice for an actor.
Understudy
An actor who learns the lines and choreography of a regular actor. In a situation when the main performer is unable to play the part, the understudy takes over.
Paper
If someone says, “The house is all paper tonight”, it means that most, if not all, of the audience have free or complimentary tickets.
Full house or Packed house
All the seats in the audience are filled to capacity.