A speech in which a character alone on stage reveals their thoughts aloud is called a soliloquy.
A soliloquy gives the audience direct access to a character’s private feelings, plans, doubts, or moral conflicts. The speaker is typically alone or believes they are alone, so the speech is not an ordinary conversation with another character. Playwrights use the device to expose information that could not naturally be revealed through dialogue.
Soliloquies became especially prominent in Elizabethan and Jacobean drama. William Shakespeare used them at crucial moments in plays such as Hamlet and Macbeth. Hamlet’s “To be, or not to be” speech, for example, presents the character’s meditation on existence, suffering, and death; Macbeth’s solitary speeches reveal his ambition and growing unease.
Soliloquy is related to, but narrower than, monologue. A monologue is any extended speech by one character and may be addressed to other people. An aside is usually a brief remark intended for the audience or another character but unheard by those on stage. Modern realistic drama uses soliloquies less often because speaking private thoughts aloud can seem unnatural, though film and television still use voice-over and direct address for similar effects.