I'm struggling to find the difference between that and what especially when using in the following sentence.
The sentence that makes me confused is:
It is concatenation that does the trick.
In the sentence above, is "that" used as a relative pronoun? Or is the whole sentence "It is..that" cleft sentence?
And why can't I use "what" instead of "that?"
Can't I write it like:
It is concatenation what does the trick.
(=What does the trick is concatenation.)
Is this grammatically wrong? If so, could you let me know the reason?
I really need your help.
Best Answer
As you said,
is a cleft sentence.
is also a cleft sentence which can also be expressed this way:
However,
is grammatically wrong because in it-cleft sentences what is not used. Instead, we use that or who when we refer to a person.