Third Conditional
Imagine a different past and its results, using 'if' + past perfect and 'would have' + past participle.
15 minUpper Intermediate
1The grammar
Use the third conditional to imagine a past that did not happen, and the result it would have had. 'If I had seen the warning, I would have left' means I did not see the warning and I did not leave.
The if-clause uses the past perfect and the main clause uses would have + past participle. Use could have when the result was possible or within someone's ability, and might have when the result was only a possibility.
The short form 'd can mean had or would. In the if-clause it means had (If I'd known), and in the main clause it means would (I'd have called). Would have can also be shortened to would've in speech and informal writing, but never write 'would of'.
In careful English, do not use would have in the if-clause. 'If I would have known' is heard in some informal American speech, but it is not accepted in standard written English.
2Structure and formation
Basic form
If + past perfect, would have + past participle
If we had booked earlier, we would have paid less.
Negative
If + hadn't + past participle, wouldn't have + past participle
If it hadn't rained, the match wouldn't have been cancelled.
Less certain result
If + past perfect, could / might have + past participle
If they had called, I could have helped.
Main clause first
would have + past participle + if + past perfect (no comma)
I would have stayed longer if I had had more time.
3Examples
If I had known about the traffic, I would have taken the metro.
I didn't know, so I didn't take the metro.
If she hadn't been so careful, the company would have lost the case.
Negative if-clause: she was careful, so the company did not lose.
We might have won if our best player hadn't been injured.
'Might have' shows that the win was only a possibility.
He could have gone to any university if he had wanted to.
'Could have' shows that this was possible for him.
What would you have done if the bank had refused the loan?
A question about an imaginary past.
If I'd had the address, I'd have sent the parcel.
The first 'd means had; the second 'd means would.
4Common mistakes
If I would have known, I would have come.
If I had known, I would have come.
Use the past perfect, not 'would have', in the if-clause.
If we left earlier, we would have arrived on time.
If we had left earlier, we would have arrived on time.
An unreal past condition needs the past perfect.
She would of called if she had known.
She would have called if she had known.
'Would of' comes from the sound of 'would've'. The correct form is 'would have'.
If he had asked, I would help him.
If he had asked, I would have helped him.
A result in the past needs would have + past participle.
5Practical usage
Regrets
Use the third conditional to talk about past mistakes: 'If I had read the contract more carefully, I wouldn't have signed it.'
Analysing results
It is useful in reviews at work: 'If we had tested the product earlier, we could have avoided the delay.'
Criticism
It can sound critical, so choose your words carefully: 'If you had told me, I could have helped' can feel like a complaint.
Now practise it
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