A cleft sentence is a complex sentence (one having a main clause and a dependent clause) that has a meaning that could be expressed by a simple sentence. Clefts typically put a particular constituent into focus. In spoken language, this focusing is often accompanied by a special intonation.
In English, a cleft sentence can be constructed as follows:
where it is a cleft pronoun and X is usually a noun phrase (although it can also be a prepositional phrase, and in some cases an adjectival or adverbial phrase). The focus is on X, or else on the subordinate clause or some element of it. For example:
Furthermore, one might also describe a cleft sentence as inverted. That is to say, it has its dependent clause in front of the main clause. So, rather than (for example):
the cleft would be: