What is the request for an actor to come to the stage to prepare for their entrance called?

The term used to refer to the request for an actor to come to the stage to prepare for their entrance is known as a "call." This is a commonly used term in theatre that indicates to the actor that they should be ready to go on stage. A call can be specific, such as a "half-hour call" or "five-minute call," indicating the amount of time before they are needed on stage. This practice ensures that actors are prepared and in the right place at the right time to maintain the flow of the performance.

The other terms listed have different meanings in a theatrical context. A "prompt" typically refers to a cue given to an actor to remind them of their lines or movements, rather than to prepare for an entrance. A "queue" is more often associated with a series of actions or a line waiting for something, and "alert" does not specifically relate to theatre jargon in the context of actors preparing for an entrance. These distinctions help clarify why "call" is the most accurate term in this situation.