9.5.5 Third conditionals



Time reference Verb in main clause Verb in conditional clause

past

would (might, could) + have + past participle

Past perfect



If we had known in advance, we would have chosen differently.
(Si ho haguéssim sabut abans, hauríem triat de manera diferent.)
They wouldn't have written the letter if they had known the facts.
(No haurien escrit la carta si haguessin conegut els fets.)
If they had been working when we came home, somebody would have seen them.
(Si haguessin estat treballant quan vam arribar a casa, algú els hauria vist.)


You will sometimes meet third conditionals without if and with the auxiliary before the subject, e.g.:



Had we known in advance, we would have chosen differently.
(Si ho haguéssim sabut abans, hauríem triat de manera diferent.)



However, you can always use the forms with if.