Third Conditional

Ever wonder “what if” about the past? The third conditional lets you do just that! It’s like rewinding time and imagining how things could have been totally different if something else had happened.

The third conditional employs had + past participle (Past Perfect) in the if-clause and subject would/could/might have + past participle in the result clause, expressing hypothetical past situations and their outcomes.

If you had come to class more often, you would have passed the test.
   ^condition                        ^result
 
If he hadn't taken his helmet, he could have died.
   ^condition                  ^result
 
If the jacket had been a bit cheaper, I might have bought it.
   ^condition                         ^result
 
I wouldn't have been late if I had not overslept.
^result                      ^condition
 
I wouldn't have arrived on time unless I had taken a taxi.
^result                                ^condition

References

• Third conditional – past unreal situations - Test-English