Explanation
Third conditional – Grammar Chart
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If clause and main clause
We use if + past perfect to talk about an imaginary or hypothetical situation in the past. And we use would have, could have or might have + past participle in the main clause to talk about the result or consequence of that imaginary situation.
- If you had come to class more often, you would have passed the test.
- If he hadn’t taken his helmet, he could have died.
- If the jacket had been a bit cheaper, I might have bought it.
Comma
As with all conditional types, we use a comma after the if–clause when it goes at the beginning of the sentence, but we don’t use a comma when the if-clause goes at the end.
- If I hadn’t overslept, I wouldn’t have been late.
- I wouldn’t have been late if I hadn’t overslept.
Unless
We can also use unless in conditional sentences to mean if … (not)
- I wouldn’t have arrived on time unless I had taken a taxi.
- = I wouldn’t have arrived on time if I hadn’t taken a taxi.
