Here are some common structures:
* One-act play: This is the simplest form, with the entire story unfolding in a single act.
* Two-act play: This is the most common structure, with the play divided into two parts.
* Three-act play: This structure was popular in the 19th century, with the play divided into three distinct parts.
* Four-act play: This structure is less common, but some plays, particularly those from earlier eras, use this format.
It's important to note that some plays may have multiple acts but also be divided into scenes within those acts.
Ultimately, the number of acts is a creative decision made by the playwright to best serve the story they are telling.