Which term is referred to as the false wall that creates a visually diminished space on stage?

The term "false proscenium" is used to describe a false wall that alters the perception of space on stage, making it appear smaller or more confined than its actual dimensions. This design technique is often employed to focus the audience's attention on the performance area, creating an intimate atmosphere. By narrowing the opening from which the audience views the action, it allows for a more concentrated experience and emphasizes the elements of the set and the actors’ performances.

The other terms do not accurately represent this concept. A back wall provides structural support and can serve as a backdrop, but it does not specifically create the same effect of diminishing space. Trim refers to decorative elements that enhance the visual appeal of the stage but do not function as a spatial modification. Side stage refers to areas beside the main performance area, often used for entrances and exits, but it does not function as a visual element to limit the audience's view in the same way as a false proscenium.