I’ll teach you, if you want.
You can leave if you like.
things that might happen in the future
8.32 When you are talking about something that might happen in the future, you use the present simple in the conditional clause, and will or shall in the main clause.
If I survive this experience, I’ll never leave you again.
Willie will never achieve anything unless he is pushed.
8.33 A more formal way of talking about a possible future situation is to use should in the conditional clause. For example, instead of saying If anything happens, I will return immediately, you can say If anything should happen, I will return immediately. In the main clause you use a modal, usually will or would.
If that should happen, you will be blamed.
Another way of talking about a possible future situation is to use were and a to-infinitive in a conditional clause. For example, instead of saying If he goes, I will go too, you can say If he were to go, I would go too. In the main clause you use would, should, or might.
If we were to move north, we would be able to buy a bigger house.
unlikely situations
8.34 When you are talking about an unlikely situation, you use the past simple in the conditional clause, and would, should, or might in the main clause.
The older men would find it difficult to get a job if they left the farm.
I should be surprised if it was less than five pounds.
If I frightened them, they might run away and I would never see them again.
In the conditional clause, were is sometimes used instead of was, especially after I.
If I were a guy, I would look like my dad.
If I were asked to define my condition, l’d say bored.
what might have been
8.35 When you are talking about something that might have happened in the past but did not happen, you use the past perfect in the conditional clause. In the main clause, you use would have, could have, should have, or might have.
Perhaps if he had realized that, he would have run away while there was still time.
If she had not been ill, she would probably have won that race.
putting the verb first
8.36 In formal or literary English, if the first verb in an if-clause is should, were, or had, this verb is sometimes put at the beginning of the clause and if is omitted. For example, instead of saying If any visitors should come, I will say you are not here, someone might say Should any visitors come, I will say you are not here.
Should ministers demand an inquiry, we would welcome it.
Were it all true, it would still not excuse their actions.
Were they to stop advertising, prices would be significantly reduced.
Had I known how important it was, I would have filmed the occasion.
8.37 Instead of using a conditional clause containing the word be, you can sometimes use a phrase consisting of if followed by an adjective or a prepositional phrase. For example, instead of saying We will sell the car, if it is necessary, you can say We will sell the car, if necessary.
This unfortunate situation is to be avoided if possible.
If I were innocent, I’d rather be tried here; if guilty, in America.
If in doubt, ask at your local library.
necessary conditions
8.38 If you want to say that one situation is necessary for another, you use provided, providing, as long as, so long as, or only if. Provided and providing are often followed by that.
Ordering is quick and easy provided you have access to the internet.
Provided that it’s not too much money I’d love to come to Spain.
The oven bakes magnificent bread providing it is hot enough.
They are happy for the world to stay as it is, as long as they are comfortable.
These activities can flourish only if agriculture and rural industry are flourishing.
When you are using only if, you can put the only in the main clause, separated from the if. For example, instead of saying I will come only if he wants me, you can say I will only come if he wants me.
He told them that disarmament was only possible if Britain changed her foreign policy.
Another way of saying that one situation is necessary for another is to use a conditional clause consisting of if followed by the subject, a form of be, and a to-infinitive clause. In the main clause, you say what is necessary using must.
It’s late, and if I am to get any sleep I must go.
If you are to escape, you must leave me and go on alone.
8.39 If you want to say that one situation would not affect another, you can use even if.
I would have married her even if she had been penniless.
Even if you don’t get the job this time, there will be many exciting opportunities in the future.
Even if is also used in concessive clauses. This is explained in paragraph 8.67.
8.40 If you want to say that a situation would not be affected by any of two or more things, you use whether. You put or between the different possibilities.
Catching a frog can be a difficult business, whether you’re a human or a bird or a reptile. Whether you go to a launderette or do your washing at home, the routine is the same.