What is the term for a signal that prompts an actor to begin their performance?

The term for a signal that prompts an actor to begin their performance is "cues." In the context of theatre and acting, cues serve as important indicators for various actions and lines within a performance. These cues can come in the form of spoken lines, physical actions, or even specific sounds that signal to the actor when they should enter, speak, or perform a particular action. The use of cues ensures that the flow of the performance remains smooth and coordinated among the cast, maintaining the overall rhythm and timing crucial to a successful show.

While "signals," "indicators," and "prompts" might be related or used in other contexts, they do not specifically denote the theatrical term associated with the actor's performance initiation as effectively as "cues" does.