Proscenium

A proscenium (Greek: προσκήνιον) is the metaphorical vertical plane of space in a theatre, usually surrounded on the top and sides by a physical proscenium arch (whether or not truly "arched") and on the bottom by the stage floor itself, which serves as the frame into which the audience observes from a more or less unified angle the events taking place upon the stage during a theatrical performance. It is a social construct which divides the actors and their stage-world from the audience which has come to witness it. A proscenium stage is structurally different from a thrust stage or an arena stage, as explained below.

Origin

In ancient Rome and Greece, the stage area in front of the scaenae frons was known as the "proscenium", meaning "in front of the scenery". In the Roman theater, no proscenium arch existed, in the modern sense. However, Roman theaters were similar to modern proscenium theaters in the sense that the entire audience had a restricted range of views on the stage—all of which were from the front, rather than the sides or back.