Conditional sentences are supposition of what will happen if some other thing happens. Conditional sentences consist of 2 clauses, main clause and if clause. Some people may be more familiar calling it only as “if clauses”. Conditional sentences are used to explain that the action in the main clause (the clause without if) can only happen if certain condition (the clause with if) is fulfilled. There are 4 types of conditional sentences:
Type 1. Possible condition
Ex: If I meet her today, I will say hi from you.
From this example, we can conclude that I can only say hi from you if I happen to meet her today. So this type means that we imagine situation in the future and both actions are possible to happen.
The pattern is using If + simple present, will + verb1
Type 2. A hypothetical condition
Ex: If he found his book, he would lend it to you.
This example means that he can’t possibly lend you the book, because he doesn’t actually find his book, it was just hypothetical.
In this type, we imagine the situation in present or future. We are implying that some condition must happen for the present or future to be different. We use past form in “if clause” to express something that opposite to the present fact, not to indicate past time. That’s why the action in main clause is very unlikely to happen whether now or in the future.
The pattern is using If + simple past, would + verb1
Type 3. An unreal past condition
Ex: If Rani had worn helmet, she wouldn’t have been hurt.
From this example, we can conclude that Rani was hurt, because the “if clause” (Rani had worn helmet) is contradicted with the fact. Rani didn’t wear helmet, and she was hurt.
In this type, we imagine different thing happened in the past that changed the result. Both the action in “if clause” and main clause are in the past. The action in main clause didn’t happen because the action in “if clause” also never happened.
The pattern is using If + past perfect, would have + verb3
Type 4. Mixed condition
Ex: If we had seen the whole accident, we would act as witness now.
This example means that we can’t act as witness now, because we didn’t see the whole accident.
In this type, we speaking about something that happened in the past but still have impact to the present or future. The main clause is related to what happen now and in future, but it can’t possibly happen because “if clause” is contradicted with the fact.
The pattern is using If + past perfect, would + verb1