It as a preparatory subject

An infinitive can be used as the subject of a clause; however, this is not very common. When the subject of a clause is an infinitive expression, we usually prefer to start the sentence with an it.

Compare:

• To talk to you is nice.

Although this sentence is grammatically correct, it doesn’t sound very natural. We can make it sound more natural by beginning the sentence with it.

• It is nice to talk to you.

More examples are given below.

• It is my ambition to become a superstar. (More natural than ‘To become a superstar is my ambition’.)

It can also be used as a preparatory subject for the for + infinitive structure.

• It is essential for the party to be a success.

Preparatory it is also used when the subject of the clause itself is another clause. A noun clause, for example, can be the subject of a clause. However, this doesn’t sound very natural.

• It seems probable that she will lose the battle. (More natural than ‘That she will lose the battle seems probable.’)
• It is essential that she should behave. (More natural than ‘That she should behave is essential.’)

It takes …. + infinitive

This structure is used to talk about the time necessary for things to happen.

• It takes me only five minutes to get dressed.
• How long does it take to get to Manchester from here?

It can also be used to emphasize one part of a sentence.

• It was John who broke the window. (Emphasis on the word John)
• It was the window that John broke. (Emphasis on the word window)