whclause

Wh-clause is a clause introduced by a wh-word (who, what, where, when, why, how, which, whose) that functions as an interrogative or a relative clause within a sentence. In English and many other languages, wh-clauses are formed through wh-movement: the wh-word moves to the front of the clause, leaving a trace at its original position. This structure underpins direct questions such as What did you see? and enables embedded questions like I wonder what you saw.

Wh-clauses also serve as relative clauses. A wh-word can function as a relative pronoun to introduce a clause that modifies a noun: The student who won the prize. In English, that, who, which, and whom can all function as relatives, with that often replacing which or who in informal contexts. Some wh-words, such as why, can appear in reason clauses like the reason why I left, where why introduces a subordinate clause rather than a standalone relative pronoun.

Cross-linguistic variation is common. English typically uses overt fronting of the wh-word and, in many cases, auxiliary inversion in questions. Other languages exhibit wh-in-situ, where the wh-word stays in its canonical position and question interpretation relies on context or intonation (as in Chinese). Still others employ different strategies for marking wh-clauses, including case marking or multiple wh-words in complex questions.

Constraints on wh-extraction exist in syntax. The movement of a wh-word is often restricted by island constraints and other locality conditions, limiting from which positions a wh-word may be extracted. Overall, wh-clauses are a central device for forming questions and for creating relative descriptions across languages.