Act  A major division in the action of a play. The ends of acts are typically indicated by lowering the curtain or turning up the houselights. Playwrights frequently employ acts to accommodate changes in time, setting, characters onstage, or mood. In many full-length plays, acts are further divided into scenes, which often mark a point in the action when the location changes or when a new character enters. (See also scene.)

The definitions in this glossary were adapted from The Bedford Introduction to Literature, Sixth Edition, by Michael Meyer