What do we call large sections of dialogue spoken by one actor?

The term for large sections of dialogue spoken by one actor is a monologue. In dramatic literature, a monologue typically involves a character expressing their thoughts or emotions aloud, often while alone on stage or regardless of the presence of other characters. This extended speech allows for a deeper exploration of a character's feelings, motivations, or intentions, providing insight into their inner world and advancing the narrative.

This understanding of a monologue distinguishes it from the other options: dialogue refers to the conversation between two or more characters, an aside is a brief remark made by a character that is intended to be heard by the audience but not by other characters, and a scene is a division of a play that indicates a specific setting or time frame during which the action takes place. Each of these elements serves a different purpose in dramatic writing, while a monologue specifically centers on the significant, sustained voice of one character.