An indefinite pronoun is a type of pronoun that does not refer to any specific person, thing, amount, or place. Instead, it refers to an unspecified or unknown entity. Indefinite pronouns are used when the identity of the subject is either irrelevant, unknown, or there are too many options to specify.

Some common examples of indefinite pronouns include:

1. **Somebody** - e.g., "Somebody left their bag here."

2. **Anybody** - e.g., "Does anybody know the answer?"

3. **Nobody** - e.g., "Nobody likes to be criticized."

4. **Something** - e.g., "I found something interesting."

5. **Anything** - e.g., "You can choose anything you like."

6. **Nothing** - e.g., "There's nothing to worry about."

7. **Everyone** - e.g., "Everyone is invited to the party."

8. **Everything** - e.g., "She lost everything in the fire."

Indefinite pronouns can be singular or plural, depending on their context and the meaning they convey. They play a crucial role in making sentences less specific or more general. Keep in mind that proper usage of indefinite pronouns is essential for clear and effective communication.