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The second conditional 

The structure of the second conditional is: if + simple past tense + modal verb

with future-in-the-past reference (e.g. would/could/might). 

In the second conditional, a speaker or writer responds to a possible or

hypothetical situation by indicating a possible outcome. The speaker or writer

states that the condition must be fulfilled for the present or future to be different:

If I knew what you wanted, maybe I could help you.

I 

would do a computer course if I had the time.

The third conditional 

The structure of the third conditional is: if + past perfect tense + modal verb with

future-in-the-past reference (e.g. would/could/might) + have + -ed participle.

In the third conditional, the speaker’s or writer’s attitude to an imagined past

situation is described. Here the speaker or writer is talking about a past event

which did not happen, and therefore things are different from how they might

have been:

If I had seen you walking, I could have offered you a lift.

Tessa 

would have been furious if she had heard him say that.

Many conditional clauses occur in these structures, but there are also several

other possible structures.

748 | Condition

Cambridge Grammar of English

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