The Third Conditional

So far we've studied the first and the second conditional, now it´s time for the third.
The third conditional is used to talk about things which DID NOT HAPPEN in the past. . It is often used to express criticism or regret. Like the other conditionals, a third conditional sentence consists of two clauses, an "if" clause and a main clause.

Jennifer explains in the following video how it is formed and used.

And if you want more practice do the following exercises:

exercise 1
exercise 2