Indefinite Pronoun Agreement

You learned in an earlier lesson that indefinite pronouns fall into three categories: some are singular, some plural, and others fall into either category depending on the context of the sentence. When using an indefinite pronoun and a possessive pronoun in the same sentence, people often choose the plural possessive pronoun their, but that's not always the correct choice. Singular indefinite pronouns take singular possessives, and plural indefinite pronouns take plural possessives.