The main difference between a monologue and a soliloquy is:
In a soliloquy, the speaker assumes they cannot be heard.
A soliloquy is a speech given by a character who is alone on stage, expressing their thoughts and feelings directly to the audience, often revealing inner conflicts or secrets. In contrast, a monologue can be directed to other characters or the audience and may not imply that the speaker is alone or unheard.