An interrogative word or question word is a function word used to ask a question, such as what, which, when, where, who, whom, whose, why, whether and how. They are sometimes called wh-words, because in English most of them start with wh-. They may be used in both direct questions and in indirect questions. In English and various other languages the same forms are also used as relative pronouns in certain relative clauses and certain adverb clauses.
