proscenium

This term is primarily used in architectural and theatrical contexts to describe the physical boundary between the stage and the audience. It evokes the concept of a "picture frame," where the action is contained within a specific rectangular space, creating a clear psychological and physical separation between the fictional world of the play and the real world of the spectators.

In modern theater criticism, the term is often used to describe the "proscenium arch" style of staging, which contrasts with "thrust" or "arena" stages. While it refers to a physical structure, it also carries a connotation of formality and traditional presentation, implying a curated view of the performance.