noun

• A place or building, consisting of a stage and seating, in which an audience gathers to watch plays, musical performances, public ceremonies, and so on.
• A region where a particular action takes place; a specific field of action, usually with reference to war.
• A lecture theatre.
• (medicine) An operating theatre or locale for human experimentation.
• (US) A cinema.
• Drama or performance as a profession or art form.
• Any place rising by steps like the seats of a theater.
• (figurative, derogatory, often following a noun used attributively) A conspicuous but unproductive display of action.