The main difference between a monologue and a soliloquy is:
A. In a soliloquy the speaker assumes they cannot be heard.
In a soliloquy, the character speaks their thoughts aloud, often when they are alone on stage, sharing their internal feelings and thoughts with the audience as if no one else is listening. In contrast, a monologue can be directed to other characters as well and does not necessarily imply that the speaker is alone or unheard.