The third conditional, also known as type III if-clause, refers to past situations and their outcomes and imagines them as different. It is also known as the impossible conditional because it talks about pasts situation that did not happen.
If you had studied harder, you would have passed this exam.
Here, the third conditional is used to talk about the past situation (studying harder) and it's outcome (passing the exam) as if they were different.
Rule 1: To form the third conditional, we use a past perfect for the if-clause, and would have + past participle for the main clause. If and would never appear in the same clause.
If my alarm had gone off, I would have managed to be at work on time.
The if-clause uses the past perfect (had gone off), and the main clause uses would have + past participle (would have managed).
Note: We can reverse the order of the clauses with no change in meaning. But, if the if-clause comes first, it should be separated by a comma. If the main clause is first, we don't need a comma.
We wouldn’t have missed our flight if there hadn’t been so much traffic.
In conditional sentences one or both classes can be negative. Here, the main clause uses the negative form of would have + past participle (wouldn’t have missed), and the if-clause uses the negative form of the past perfect tense (hadn’t been).
The order of the clauses is reversed without changing the meaning of the sentence.
Rule 2: We can use the modal verbs could and might instead of would in the third conditional, but we do not use should.
If he had studied medicine, he could have been a doctor now.
Here, we use could have + past participle for the main clause instead of would.
Rule 3: We can use the third conditional to express regrets.
If I had been more confident, I would have asked for a higher salary.
Third conditional is used to express regrets about not being confident enough.
Rule 4: We can use the third conditional to give feedback and criticize.
This essay would have been better if you had included more examples.
Third conditional is used to give feedback on someone's assignment.
Rule 5: We can use the third conditional to reflect on the past.
If I hadn't applied for an international internship, I wouldn't have met so many fantastic people.
Third conditional is used to reflect on the past event and its outcome as if they were different.
Choose the correct option to form the third conditional. If you had told me about the meeting, I would have ___.