Complex Sentences with Subordinate Clauses of Condition

There are three main types of conditional sentences.

First conditional (or Type 1 conditional) is used to talk about something that will or will not (probably) happen in the future. The condition is quite likely to be fulfilled:

If he finishes work early, he will go home.

present simple future simple

• We can use all present tenses after if, not just the simple present:

If he has finished work by 4 o’clock, he will go home.

• We can use all future tenses in the main clauses, not just the future simple:

If he doesn’t hurry, the plane will have left by the time he gets to the airport.

• When we use will in the main clause, we are expressing certainty or near-certainty:

If the weather clears, we’ll go for a walk. (certain, or near-certain)

If we do not feel “certain” enough to use will, we can use another modal to say what is possible, necessary or desirable:

If it’s fine tomorrow, we may go for a swim. (it’s possible)

If it’s fine tomorrow, we must go for a swim. (it’s necessary or desirable to do this)

• If + should, instead of if + present simple, makes the condition more doubtful or very polite:

If I should see him, I’ll ask him to ring you. (Cf: If I see him, I’ll ask him to ring you.)

• We can use the imperative in place of an if-clause to comment, threaten, request, etc.

We follow the imperative with and in place of an if-clause in the affirmative:

If you fail to pay, they’ll cut off the electricity. – Fail to pay and they’ll cut off the electricity.

We follow the imperative with or in place of an if-clause in the negative:

If you don’t stop borrowing money, you’ll be in trouble. – Stop borrowing money, or you’ll be in trouble.

Second conditional (or Type 2 conditional) is used to talk about a present situation which is impossible:

If my parents were alive, they would be very proud of me now.

past simple would+infinitive

• We sometimes use Type 2 conditional to describe something that is reasonably possible. The

past tense form does not refer to past time:

If you went by train, you would get there earlier.

• We use were in place of was after if in all persons (Subjunctive II):

If I were better qualified, I would apply for the job.

We use If I were you and If I were in your position to give advice. We can also refer to somebody else:

If I were in Jane’s position, I’d look for a new job.

• When we use would in the main clause, we are expressing as much certainty as possible:

If he knew the facts, he would tell us what to do. (certain, or near-certain)

If we do not feel “certain” enough to use would, we can use another modal to say what would be possible or necessary:

If he knew the facts, he might tell us what to do. (it’s possible)

If he knew the facts, he should tell us what to do. (it’s necessary)

Third conditional (or Type 3 conditional) is used to talk about something in the past that did not happen:

If she had worked harder, she would have passed the exams.

past perfect would+perfect infinitive

If I had been trying harder, I would have succeeded.

past perfect continuous would+perfect infinitive

• We often use If I had been you and If I had been in your position to describe what we would have done in someone else’s position:

If I had been you, I would have accepted their offer.

• When we use would have in the main clause, we are expressing as much certainty as possible:

If he had known the facts, he would have told us what to do. (certain, or near-certain)

If we do not feel “certain” enough to use would have, we can use another modal to say what would have been possible:

If he had known the facts, he might have told us what to do. (it’s possible)

If he had known the facts, he could have told us what to do. (he would have been able)

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Mixed conditionals

We do not always have to stick rigidly to the “three types of conditional sentences”. There are occasions when we can use any tenses in if-clauses, depending on the context:

If I am as clever as you say I am, I would have been rich by now. Type 1 + Type 3

If you knew me better, you wouldn’t have said it. Type 2 + Type 3

If I had had your advantages, I would be better off now. Type 3 + Type 2