Pronouns are substitutes for nouns or other pronouns. The word(s) that a pronoun refers to is called its antecedent.

A pronoun must agree with its antecedent. A singular pronoun must have a singular antecedent, A plural pronoun must have a plural antecedent. The rules for a pronoun’s agreement with its antecedent are similar to the rules for agreement of subjects and verbs. Here are three of the common basic rules that apply to pronoun agreement:

1. When two or more antecedents are joined with or or nor, the pronoun agrees with the closer antecedent.
        Example: Neither of the Casey twins nor Ben will lend me his marketing notes.

2. Use a plural pronoun to refer to two or more antecedents joined with and.
        Example: The manager and her assistant will take three of their vacation days to attend the High-tech Show.

3. Use a singular pronoun to refer to pronoun antecedents such as either, neither, each, every and any pronoun ending in -one, -body, or -thing.
        Example:Does everyone want chopped nuts on his or her ice cream?
Each of the children liked his or her kindergarten teacher.

4. Use a plural pronoun to refer to antecedents such as both, several, many, few which are always plural.
        Example: Several of the candidates will share their ideas tonight.

5. Ignore prepositional phrases that come between a pronoun and its antecedent.
        Example: My manager or one of his friends will lend me his squash racket for the game.