Most, but not all, indefinite pronouns are singular. When an indefinite pronoun is the subject of a sentence, it has to agree in number with the sentence’s verb. Indefinite pronouns can switch between the subjective and the objective case and don’t change form when they do.

An indefinite pronoun can refer to all of something, something singled out from a group, a range of possibilities, one nonspecific person or thing, an absence, or a nonspecific amount or quantity.

Pronouns can be categorized into many types, all of which are very commonly used in English: · Personal pronouns · Subject and object pronouns · Possessive pronouns · Reflexive pronouns and intensive pronouns · Impersonal pronouns · Demonstrative pronouns · Interrogative pronouns · Relative pronouns · Indefinite pronouns · Reciprocal pronouns · Dummy pronouns (expletives)