Discourse functions of the wh-cleft
1 What we want is WATney’s.
This was a famous advertising slogan, at one time, for Watney’s beer. It is clearly much more emphatic than the plain version 2 and even more than the it-cleft 3.
2 We want WATney’s.
3 It’s Watney’s (that) we want.
In both types of cleft there is presupposed information: in this case, that we want something. But while the it-cleft 3 suggests contrast (Watney’s, not other beers), the wh-cleft 1 suggests exclusiveness. (It’s ONLY Watney’s we want, and no other). The wh-cleft consists of a wh-word, of which by far the most common is what, followed by a clause containing Given or presupposed information, then a form of be, followed by the New information:
//What we want// (it is presupposed: that we want something) is
Watney’s//Given New
This structure is also sometimes called a thematic equative, since it is of the form ‘X = Y’.
