When you want to say that one situation (described in the main clause) depends on another situation, you use a conditional clause. Conditional clauses usually begin with if or (for negative clauses) unless.
Jane will pass the exam if she works hard.
Jane will not pass the exam unless she works hard.
They may follow or go in front of the main clause.
If Jane works hard, she will pass her exam.
Conditional clauses are used in two main ways:
– If you see the situation as a real one, and likely to happen, you use the present simple tense in the conditional clause and will (‘ll) or won’t in the main clause. Don’t use will in the conditional clause.
If you take a taxi, you will be there in good time. NOT If you will take a taxi…
If you wear a coat, you won’t get cold. NOT If you will wear a coat…
– If you see the situation as unreal, imaginary, or less likely to happen, you use the simple past tense in the conditional clause and would (‘d), might, or could in the main clause. Don’t use would in the conditional clause.
If you saw a ghost, what would you do? NOT If you would see a ghost…
If I bought a new coat, I might not feel so cold. (=I would possibly not feel so cold)
If I found their address, I could write to them. (=I would be able to write to them)
In sentences of this kind, the past tense of the verb be appears as were after the first and third persons, in formal speech and writing. Only use was in informal speech.
If I were at home, I would be watching television. (informal: If I was at home…)
If John were playing today, we’d have a chance of winning. (informal: If John was playing…)
– If you want to talk about conditional situations in the past, use had (‘d) in the conditional clause, and would have in the main clause.
If I’d seen her, I would have asked her to call. (=I did not see her)
The books wouldn’t have been damaged if Mary had moved them. (=”Mary” didn’t move them)
– You can use when instead of if in sentences of the first type (present simple + will etc), but not with those of the second (simple past + would etc). When is not used in situations that are unlikely or impossible.
What will John do if he goes home? (=”John” is probably going home) OR What will John do when he goes home? (=”John” is definitely going home)
What would John do if he went home? (=”John” is probably not going home) NOT What would John do when he went home?
I would shout if I saw a ghost. NOT I would shout when I saw a ghost.
If you want to talk about a situation in the present which you are not happy about, and would like to change, use the simple past tense in the conditional clause.
I wish I had a new bike. (=”unfortunately,” I don’t have a new bike)
If you want to talk about a situation in the past which you are not happy about, and would like to change, use had in the conditional clause.
I wish I’d gone by train. (=”unfortunately,” I didn’t go by train)
I wish I hadn’t gone by train. (=”unfortunately,” I did go by train)