Afterpieces is a term used to describe the concluding act of a play or performance. The antonyms for afterpieces are, therefore, the opening acts or prologues. Prologues are introductions that provide context or background information about a performance, while afterpieces conclude it. Other antonyms for afterpieces might include preludes, overtures, or beginnings. Each of these terms suggests the start of an event or performance, whereas afterpieces refer to the end. Understanding these antonyms can help one appreciate the structure and design of a play or performance, and better understand how it is constructed.