What is the purpose of a soliloquy?

an act of speaking one's thoughts aloud when by oneself or regardless of any hearers, especially by a character in a play

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Whereas a novel can describe a character’s unspoken thoughts, a play contains no such description. To overcome this limitation, a playwriter uses soliloquies. The character expresses his or her inner thoughts aloud, in the absence of other characters. Only the audience can hear what the character says.

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