What is an interrogative pronoun?

An interrogative pronoun is a pronoun that is used to introduce a question. The main English interrogative pronouns are what, which, who, whom, and whose.

They can be used in a direct question, which ends in a question mark (e.g., “What is your favorite color?”) and indirect questions, which don’t have a question mark (e.g., “I asked what her favorite color was”).