1. A building or outdoor area in which dramatic performances are presented: Theaters are places where plays or motion-picture shows are shown.

The medical students, including Mike and James, watched the operation procedures from a glass-enclosed theater.

2. The activity or the profession that involves acting in, producing, directing, or writing plays: Mr. Carter has been successful for years in the vocation of the theater as a director and producer.

The entire theater gave the stars a standing ovation for their outstanding performances.

3. A play or other presentation which is considered in terms of its dramatic quality: This has been a very humorous and entertaining theater tonight.

Mrs. Miller told her students, that Shakespeare's "Hamlet" is one of the best theaters they could ever see.

4. A room or hall for lectures, speeches, etc.: The university theater has seats that are arranged in tiers (several rows or floors arranged in different levels) where classes are held.
5. An area where something happens or is taking place: The army has opened a new theater of battle.

The South Pacific was a significant theater for much of the action in World War II.

During the presidential-debating theaters, members of the same political party were attacking each other instead of concentrating on the opposing political candidates.

6. Etymology: borrowed from Old French theatre, a learned borrowing from Latin, and borrowed directly into English from Latin theatrum, from Greek theatron, "a place for seeing shows".

The standard Canadian and British spelling for this word entry is theatre; in fact, it is popular throughout the English-speaking world, although the standard U.S. spelling is theater.