Here's a breakdown:
* Pronoun: A word that replaces a noun (e.g., he, she, it, they, someone, everything).
* Antecedent: The noun or noun phrase that a pronoun refers to.
Indefinite pronouns refer to nonspecific people, places, or things. Examples include:
* Someone, anyone, everyone, no one
* Something, anything, everything, nothing
* All, some, any, none
* Each, either, neither
Example:
* Someone knocked on the door. (We don't know who knocked.)
In this case, "someone" is an indefinite pronoun because it doesn't have a specific antecedent. We don't know who knocked on the door.
Note: While indefinite pronouns don't have a specific antecedent, they still need to agree in number with the verb in a sentence. For example, "Everyone is welcome" (not "Everyone are welcome").