Another lesson on the third conditional is in Level 490 - Upper Intermediate.
The third conditional (also called conditional type 3) is a structure used for talking about unreal situations in the past. This page will explain how the third conditional is formed, and when to use it.
The structure of a third conditional sentence
Like the other conditionals, a third conditional sentence consists of two clauses, an “if” clause and a main clause:
|IF clause||main clause|
|If I had studied harder,||I would have passed the exam.|
Explanation: I failed the exam, because I didn't study hard enough.
If the “if” clause comes first, a comma is usually used. If the “if” clause comes second, there is no need for a comma:
|main clause||IF clause|
|I probably would have passed the exam||if I had studied harder.|
We use different verb forms in each part of a third conditional:
|IF clause||if + subject + past perfect verb*|
|main clause||subject + would (OR could, OR might) have + past participle|
*The past perfect is formed with the auxiliary verb “had”, and the past participle (or third form) of the verb.
Note also that third conditional forms can be contracted:
|Full form||If I had studied harder, I probably would have passed the exam.|
|Contracted form||If I'd studied harder, I probably would've passed the exam.|
Using the third conditional
The third conditional is used to talk about things which did not happen in the past. If your native language does not have a similar construction, you may find this a little strange, but it can be very useful. It is often used to express criticism or regret:
|If you had driven more carefully, you would not have had an accident.||Criticism: You had an accident because you didn't drive carefully enough.|
|If we had played a little better, we could have won the game.||Regret: We didn't play well, so we lost the game.|
|If you had saved your money, you could have bought a computer.||Criticism: You didn't save your money, so now you can't afford a computer.|
|If it had snowed, we could have gone skiing.||Regret: It didn't snow, so we couldn't go skiing.|