A theater, theatre or playhouse, is a structure where theatrical works or plays are performed or other performances such as musical concerts may be produced. While a theater is not required for performance (as in environmental theater or street theater), a theater serves to define the performance and audience spaces. The facility is traditionally organized to provide support areas for performers, the technical crew and the audience members.
The most important of these areas is the acting space generally known as the stage. In some theaters, specifically proscenium theaters, arena theaters and amphitheaters, this area is permanent part of the structure. In a blackbox theater the acting area is undefined so that each theater may adapt specifically to a production.