A theater is a building where actors perform plays, musicals, and other live performances for an audience. When you go to the theater, you sit in rows of seats facing a stage where performers bring stories to life right in front of you, without cameras or special effects.

Theater also means the art form itself: the whole world of creating and performing plays. Someone who loves theater might act in school productions, design costumes and sets, or write scripts. Theater has existed for thousands of years, from ancient Greek tragedies to Shakespeare's comedies to modern Broadway musicals. Unlike movies, theater happens live, which means every performance is slightly different and the actors can feel the audience's reactions in real time.

In British English, people spell it theatre, which you'll see in names like the Globe Theatre in London. Americans sometimes use theatre too, especially in formal names like the Guthrie Theater.

The word also appears in phrases like theater of war, meaning the region where military operations take place.