Grammar / B1 Grammar lessons and exercises / Third conditional: Past unreal situations
Third conditional grammar chart explaining sentence structure for past hypothetical situations with examples like "If you had come to class, you would have passed the exam."

We use the past perfect in the if-clause of a third conditional sentence 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.
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.
We can also use unless in conditional sentences to mean if … (not)