Cleft Sentences

Cleft Sentences are a way of emphasising particular words or expressions

What and Who
ex.:
Mary kept a pig in the garden shed.
Mary was the person who kept a pig in the garden shed.
The person who kept a pig in the garden shed was Mary
A pig was what Mary kept in the garden shed.
What Mary kept in the garden shed was a pig.

-Mary and a pig are the words we want to emphasise.
-Is/Was is the verb that links the emphasised word
-and the expression the person who/what
->to the relative clause

The place where, The day when, The reason why
ex.:
The place where Mary kept a pig was the garden shed.
Tuesday was the day when Jake went to London to see Colin.
The reason why Jake went to London on Tuesday was to see Colin.

Verbs
ex.:
What she did was to scream.
What he does is write science fiction.
What I'll do is, I'll call John and ask his advice.

Whole Sentences
ex.:
What happened was (that) the car broke down.

Other structures
All (that) and expressions with thing can be used in cleft sentences.
ex.:
All I want is a house somewhere sunny.
The only thing I remember is a terrible pain in my head.
My trip to Thailand was definitely something.
It was not until I met you that I knew real happiness.
It was only when I read her letter that i realised what was happening.

Preparatory IT

It is I who/ It is me that