wh-movement

In linguistics, wh-movement (also known as wh-fronting, wh-extraction, or wh-raising) is the formation of syntactic dependencies involving interrogative words. An example in English is the dependency formed between what and the object position of doing in "What are you doing?". Interrogative forms are sometimes known within English linguistics as wh-words, such as what, when, where, who, and why, but also include other interrogative words, such as how. This dependency has been used as a diagnostic tool in syntactic studies as it can be observed to interact with other grammatical constraints.

In languages with wh-movement, sentences or clauses with a wh-word show a non-canonical word order that places the wh-word (or phrase containing the wh-word) at or near the front of the sentence or clause ("Whom are you thinking about?") instead of the canonical position later in the sentence ("I am thinking about you"). Leaving the wh-word in its canonical position is called wh-in-situ and in English occurs in echo questions and polar questions in informal speech.