What is a major division in play script called?

A major division in a play script is called an act. An act is a self-contained section of a play, typically comprising multiple scenes. Acts are used to structure the play and allow for dramatic development, suspense, and resolution. For example, a three-act play might have the first act introduce the characters and setting, the second act present a conflict or challenge, and the third act lead to a conclusion or resolution. The division into acts helps in structuring and pacing the story progression in a play script.