The third conditional (also called conditional type 3) is a structure used for talking about unreal situations in the past. This is the way we imagine how things could have been different in the past.
When to use the third conditional
We use the third conditional to talk about:
- Things that did not happen;
- Situations like dreams or wishes with no possibility of coming true.
- If I’d known, I would have worn something nicer.
- He wouldn’t have missed the bus if he hadn’t overslept.
When we use the third conditional, we are talking about an impossible past condition. The condition was not and cannot ever be true because it is over and in the past. This also means the result is impossible because the condition is impossible.
How to form the third conditional
The third conditional contains:
- An ‘if’/condition clause
- A main/result clause
- If she had won the lottery, (‘if’/condition clause) + she would have bought a new house. (result clause)
- I would have told her about it (result clause) + if I had known. (‘if’/condition clause)
Just like the second conditional, the ‘if’/condition clause has a comma at the end if it comes first. There is no comma if the ‘if’/condition clause comes second, after the result clause.
- I would have done better on the test if I had studied harder. (no comma needed because the “if” clause comes second)
- If you had tried harder, you would have won. (a comma comes after the “if” clause when it is first)
We can make positive, negative, and interrogative sentences using the third conditional. We can also use ‘should have‘, ‘could have‘, and ‘might have‘ with modals.
- If we had worked better as a team, we might have won the tournament.
- You could have bought that toy if you had saved your money.
- If it had rained yesterday, what would you have done?
- Your day would have been better if you had not stayed up all night playing games.
We can also use the contracted form in each clause.
- You could’ve bought that computer if you’d saved your money.
- If she’d tried harder, she’d have done better.
- If you hadn’t slept in, you wouldn’t have missed your flight.
Let’s summarize different types of conditional sentences:
Here’s a good video from Learn English on Skype explaining when and how to use the third conditional:
Read more on conditionals: