Pronouns are used in place of nouns to avoid repetition. There are several types of pronouns including personal pronouns that change form based on gender, number, and case; demonstrative pronouns like this and that; interrogative pronouns like who and what that are used to ask questions; relative pronouns like who and which that join two clauses; and indefinite pronouns like anyone and everything that refer to unspecified people or objects. Pronouns can also be reflexive to refer back to a noun in the same sentence or reciprocal to show two nouns acting in the same way toward each other.