The 3rd Conditional is also called the past unreal conditional.  
This conditional is used in the past.    


STRUCTURE

If  +  Subject  +  Had  +  Past Participle,
+  Subject  +  Modal  + Have + Past Participle


Examples:        

Could
If I had known about the party, I could have gone.

Should
If you had known about the party, you should have told me.

Might
If he had known about the party, he might have gone.

Would
If I had known about the party, I would have gone.


USES

Imaginary situations in the past
This includes actions that did not happen in the past.  

Examples:  
  • If I had gone to university, I would have studied medicine.
  • If You had gone to the party, you would have met him.


Advice in the past
These sentences usually don't have an "if" clause, and can
often be more direct.

Examples:  
  • You should have saved your money.
  • You should not have gone with him.


Describes what you would have done differently

Example:  
  • If I had been you, I would not have bought those shoes.
  • If I had thought about it, I wouldn't have eaten so much.


Questions

Here are some examples of questions with the 3rd conditional:

  • What would you have done if you had been me?
  • Would you have finished if you had had more time?
  • Would you have bought something cheaper?
  • Should we have paid more attention in class?




Practice the 3rd conditional with these tests:

3rd Conditional Test

3rd Conditional Test 2

2nd vs. 3rd Conditional Test

For 3rd conditional music, try these songs:

Taylor Swift - Should've Said No

Brian McKnight - Shoulda, Woulda, Coulda
Conditional Tests

Zero Conditional

Business English
Conditional Music