A wh-cleft is a grammatical construction in which a constituent is highlighted by putting focus on the end of the sentence. This is achieved by starting the sentence with a wh-clause (usually beginning with what, though other wh- words are found as well). Emphasis in a wh-cleft is put on what follows the sentence-initial wh-clause: What I need is sleep. The highlighted constituent does not feature in its normal place with respect to the other constituents in the sentence. (AEG Ch. 6)
wh-Constituent
A wh-constituent is a constituent that starts with a wh-word: which book, what course, who. Recall that how is a wh-word as well, so how quickly is also a wh-constituent. (AEG Ch.2)
wh-Interrogative, see information interrogative clause
