Provide the definition of a pronoun.
A word that can function by itself as a noun phrase and that refers either to the participants in the discourse (e.g., I, you) or to someone or something mentioned elsewhere in the discourse (e.g., she, it, this).
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Provide the definition of a pronoun.

### Response:
A word that can function by itself as a noun phrase and that refers either to the participants in the discourse (e.g., I, you) or to someone or something mentioned elsewhere in the discourse (e.g., she, it, this).