What is the term for a long speech by one character in a play?

A long speech by one character in a play is referred to as a monologue. This term specifically denotes a situation where a single character speaks at length, often expressing their thoughts, feelings, or reflections directly to the audience or other characters. It serves various purposes, such as character development, advancing the plot, or revealing inner conflicts.

In contrast to a monologue, dialogue involves an exchange between two or more characters. Soliloquy, while similar to a monologue, is characterized by a character speaking their thoughts aloud while alone on stage, typically revealing their inner motivations without the influence of other characters. An aside, on the other hand, is a brief remark made by a character intended to be heard by the audience but not by other characters, often revealing hidden thoughts or providing commentary.

Thus, the distinctive aspect of a monologue is its length and the context of being delivered directly to the audience or characters, which makes it the correct choice for this question.