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. This focusing is often accompanied by a special intonation.
In English, a cleft sentence can be constructed as follows:
it + conjugated form of to be + X + subordinate clause
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).
Noun: It's money that I love.
Prepositional phrase: It was on foot that he went there.
Adverbial phrase: It was greedily and speedily that Homer Simpson drank his beer.
Non-finite clause: It is to address a far-reaching problem that Oxfam is launching this campaign.
Gerund: It could be going home early or slacking off work that the boss reacted to.
Adverbial clause: It was because she was so lonely all the time that she decided to move out.
English is very rich in cleft constructions. Below are examples of other types of clefts found in English, though the list is not exhaustive (see Lambrecht 2001 for a comprehensive survey, Collins 1991 for an in-depth analysis of it-clefts and wh-clefts in English, and Calude 2009 for an investigation of clefts in spoken English).
It-cleft: It is Jaime for whom we are looking.
Wh-cleft/Pseudo-cleft: What he wanted to buy was a Fiat.
Reversed wh-cleft/Inverted pseudo-cleft: A Fiat is what he wanted to buy.
All-cleft: All he wanted to buy was a Fiat.
Inferential cleft: It is not that he loves her. It's just that he has a way with her that is different.
There-cleft: And then there's a new house he wanted to build.
If-because cleft: If he wants to be an actor it's because he wants to be famous.
И на закуску
WHAT-CLAUSE + BE + PHRASE
Pseudo-cleft sentences (also called wh-clefts) are similar in function to cleft sentences, but they are formed with the pronoun what (= the thing(s) that/which). The emphasis in a pseudo-cleft sentence is on the phrase after the what-clause + be:
What you need is a good sleep.
If we want to refer to a person, we say The person/people who/that:
The people who/that I met were members of the delegation.
If we want to emphasise an action, the verb after be usually takes the form that corresponds to the form used in the what-clause:
What you should do is write a letter to the manager.
What they were doing was arguing about which train to take.
In the following examples, the verb after be takes the form that the verb in the what-clause is normally followed by:
What I want is to sleep.
What he can't stand is getting up early.
In the past simple and present perfect, we can use the following patterns:
What I did in the end was (to) go home.
What I have done is (to) write a letter to the editor.
http://www.grammaring.com/pseudo-cleft-sentences More
I will start this article with describing a kind of relative clause that is called 'cleft sentence'. "Cleft" means in this sense "divided" because in the transformations below you will find some division between subject and verb seen in the cleft sentence. These transformations are really useful in writing (and of course in speaking too :)) because they allow us to transfom a sentence in a way that can be very convenient for us when we want to emphasize some parts of the sentence.
The following examples are considered to be more formal, however we can also hear them in less formal dialogues as well, so here the distinction between formal and informal English might not necessarily be valid.
(In italics I put what I initially want to be emphasized, in bold - the part of the sentence that is emphasized in a cleft sentence)
Harry turned out to be a thief.
Harry is the person who turned out to be a thief. (To) Harry jest osobą, która okazała się być złodziejem.
The person who turned out to be a thief was Harry. Osobą, która okazała się być złodziejem jest Harry.
These are the ways of placing the emphasis on subject. The same can be done in the case of object:
Harry turned out to be a thief.
A thief was what Harry turned out to be. Złodziej był tym kimś, kim okazał się Harry.
What Harry turned out to be was a thief. Kim okazał się być Harry był (zwykły) złodziej.
Analogically, the same refers to verb:
Harry stole the car.
What Harry did was (to) steal the car. To co zrobił Harry to kradzież samochodu.
What is also possible is to put extra emphasis on the whole sentence by using a cleft structure with 'what' and some verb. It is illustrated in the examples below:
The car was stolen.
What happened was (that) the car was stolen. To co się stało to kradzież samochodu.
She said she would give up smoking.
What she said was (that) she would give up smoking. (To) co powiedziała,to to, że rzuci palenie.
We can also find cleft constructions which make use of preparatory it. Again, we can emphasize whichever part of the sentence, depending on the need or purpose of the author.
My sister sent a postcard to her teacher yesterday.
It was my sister that sent a postcard to her teacher yesterday. To moja siostra wysłała kartkę swojemu nauczycielowi.
It was a postcard that my sister sent to her teacher yesterday. Pocztówka była tym, co moja siostra wysłała swojemu nauczycielowi.
It was my sister`s teacher that she sent a postcard to yesterday. To do swojego nauczyciela moja siostra wysłała kartkę.
It was yesterday that my sister sent a postcard to her teacher. To wczoraj moja siostra wysłała swojemu nauczycielowi kartkę.
When we want to emphasize a pronoun as subject, we have two ways out:
It is I who am responsible for the accident. (FORMAL)
It is me that is/who is responsible for the accident. (INFORMAL) To ja jestem odpowiedzialny za wypadek.
It is you who are wrong. (FORMAL)
It is you that is wrong. (INFORMAL)
It is also possible to use cleft sentences when we want to emphasize a place, time or reason. Let`s look at these sentences:
John sleeps in the attic.
The attic is where John sleeps.
The attic is the place where John sleeps.
The place where John sleeps is the attic.
John went to London on Tuesday.
Tuesday was the day when/that John went to London.
John went to London to see Jane.
To see Jane was the reason why John went to London.
The reason why John went to London was to see Jane.
Let`s remember that sentences like these:
All you need is love.
All (that) I did was (to) touch the button and the car exploded.
The only thing I remember is a big black spider.
My FCE exam is something (that) I will never forget.
This is what he did to save the house.
are also examples of clefting. What clauses are sometimes referred to as 'pseudo-cleft' sentences, but for the time being we do not need to know why etc. It`s just worth remembering and that`s it:)
As regards emphatic structures, let`s also remember about two more things. The first thing is the use of the auxiliary 'do' to provide an emphatic effect:
I do promise to help you. Naprawdę obiecuję pomóc.
It does seem to be true. To naprawdę wydaje się prawdziwe.
Another thing is the use of reflexive pronouns as emphatic pronouns:
I want to repair this radio myself (=on my own). Chcę sam naprawić to radio.
Kate herself opened the window. Kasia sama otworzyla okno.
http://pleasure-of-english.blogspot.com/2012/08/53-emphatic-structures-ii-cleft.html