Many indefinite pronouns, such as everyone and each, are always singular.

When antecedents are joined by or or nor, the pronoun must agree with the closer antecedent.

A collective noun can be either singular or plural, depending on whether the people are seen as a single unit or as multiple individuals.

With a singular antecedent that can refer to either a man or a woman, you can use his or her, he or she, and so on. You can also rewrite the sentence to make the antecedent and pronoun plural or to eliminate the pronoun altogether.

Pronouns must agree with their antecedents in gender (for example, using he or him to replace Abraham Lincoln and she or her to replace Queen Elizabeth) and in number. (See 34f.)