Glossary of theater terms

• Act: A division of a play, may be further broken down into "scenes". Also, what the performers do on-stage.
• Ad-lib: When a performer improvises line on-stage. Derived from ad libitum.
• Aisle: An open space amongst seating for passage.
• Alternate: see Understudy.
• Amphitheater: an open-air theater, with seats rising in curved rows.
• Angel: An individual or organization which provides financial support for a production.
• Apron: The front area of the stage, nearest the audience; the portion of the stage in front of proscenium arch.
• Aside: A line spoken by an actor/actress directly to the audience, unheard by the other performers on-stage.
• Assistant director: Works very closely with the director and with the cast. They will gather research on the production, help keep the production true to the director's vision and help lead rehearsals should the director not be able to attend.
• Assistant stage manager: Assists the production stage manager, with everything from taping floor plan marking to making sure that everyone has a copy of the script. They also make sure that the set has the needed props. Before a rehearsal the assistant stage manager helps the stage manager make sure everything is ready. At the end of rehearsal the assistant stage manager along with the stage manager will make sure that the space is locked up. Often shortened to ASM.
• Audition: The activity where actors/actresses perform for the director or casting director, in order to obtain roles in a production.
• Auditorium: The portion of a theater which contains the audience seating.
• Avante Garde: Experimental or innovative works or people, derived from the French.
• Balcony: An elevated portion of seating in the back of the auditorium.
• Curtain Call: At the end of a live performance the cast will come out and do a bow while the audience applauds.
• Doubling: When an actor plays more than one character in a production. Most times this is done for economical reasons but it can be that because an actor would like to take on more than one role in the performance.
• Understudy: A person who learns the part of a specific character or characters. Should the performer who is cast in those roles be unable to perform their part due for any reason, the understudy will step in and perform the role. Also known as an Alternate.