Just like nouns, the pronouns used in place of them have four properties: number, person, gender, and case. Pronouns should agree with their antecedents in number, person, and gender. Let’s first look at how pronouns agree with their antecedents in number—you’ll find that much of the same logic that guides subject-verb agreement applies to antecedents-pronouns as well.
The number of a pronoun must match that of its antecedent noun or nouns. If the antecedent is singular, its pronoun is singular; if the antecedent is plural, its pronoun is plural:
This weekend, Sandra celebrated her birthday with a bad-poetry party.
Guests were instructed to bring along their favorite bad poems to read aloud at the party.
In the first example above, Sandra is singular, so the singular pronoun her is used. Likewise, guests is plural, so the plural their is used.
If two or more singular nouns or pronouns are joined by and and together serve as the antecedent for a pronoun, you have a plural antecedent, so a plural pronoun should be used:
Sandra and her roommate hosted the party at their house.
A collective noun that describes a group—such as audience, class, or team—takes a singular pronoun if the members of the group are acting as a single unit:
The crowd at the party showed its appreciation for the bad poetry by both applauding and booing.
The Chicago Manual of Style advises that a collective noun can take a plural pronoun if the members of the group act individually, but personally I always rewrite the sentence so there is no appearance of error:
The audience enjoyed reading their poems for each other.
The guests enjoyed reading their poems for each other.
Finally, if a singular noun is preceded by two or more adjectives that suggest different types or facets of the noun, you may use a plural pronoun:
Good and bad poetry may have more in common than their readers are willing to admit.
Where There’s a Rule, There’s an Exception
Of course, there are exceptions to every rule, and when it comes to pronoun number, there are several. However, once again, the rules that guide subject-verb agreement are useful when it comes to pronouns and their antecedents.
First, you might have two or more singular antecedents joined by and that actually refer to the same person or thing. In this case, use a singular pronoun:
Sandra was grateful to her best friend and roommate for all of her hard work before, during, and after the party.
You also might have two or more singular antecedents that are joined by and but preceded by each, every, or no. The pronoun is singular in this case as well:
Every plate and cup was washed and put back in its rightful place by the end of the night.
If you have two or more singular antecedents joined by or, nor, either–or, or neither–nor, use a singular pronoun:
Neither Sandra nor her roommate shirked her responsibility to clean up after the party.
If, however, you have two or more antecedents of different numbers joined by or or nor, the pronoun should agree in number with the antecedent closest to it. It’s easier to adhere to this rule if the sentence is written so any plural antecedents follow the singular antecedents:
If Sandra or her guests had a bad time, they didn’t say so.
Finally, if you have two or more antecedents of different numbers joined by and, use a plural pronoun, no matter what order the antecedents appear in:
The guests and the birthday girl were still talking about what a good time they had days after the party.
Do you have a question about pronouns? Let me know, and I’ll include it in a future installment of Mots Justes’ ongoing series.
The Mots Justes Series on Pronouns
Chicago Manual of Style, The. 15th ed. Chicago: The University of Chicago Press, 2003.