Conditional and If Sentences

What is always true: present + present

Both present tense simple and continuous are possible after if meaning when

If I work late, I get tired.

If the water is boiling, it means that the food is nearly ready.

What was always true: past + past

Both past simple and continuous are possible after if meaning when

We went home early if it was foggy.

If it was snowing, we stayed at home.

Real situations: present + will

Here we think that the outcome is really possible.

If you keep driving like that, you’ll have an accident.

Hypothetical situations: past + would

These are imaginary situations.

If I knew the answer, I’d tell you.

The verb be usually takes the form were for all persons in these sentences, though was is used in everyday speech. Note that in the first person it is possible to use should instead of would.

If I left home, I think I should be lonely.

Hypothetical past situations: past perfect + would have

These refer to past events.

If I had known you were coming, I would have met you at the station.

With modals

Possible situations in the present

If you get wet, you should change your clothes immediately.

If you come early, we can discuss the problem together.

Hypothetical situations

If I had the money, I could help you.

Hypothetical past situations

If you hadn’t reminded me I might have forgotten.

If only

This adds emphasis to hypothetical situations. With past events it adds a sense of regret. The second part of the sentence is often left out.

If only I had enough time!

If only I hadn’t drunk too much, this wouldn’t have happened!

Unless and other alternatives to if

Unless means only if not. Not all negative if sentences can be transformed into unless sentences.

If he wasn’t told by Jane, he couldn’t have known

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Unless he was told by Jane, he couldn’t have known. (can be changed)

If Mr. Smith doesn’t come back, he’ll phone you. (cannot be changed)

If one situation depends on another, if can be replaced by as/so long as, provided or only if.

I’ll do what you say provided the police are not informed.

Even if describes how something will happen whatever the condition.

Even if it rains, we’ll still go for a picnic.

Past events with results in the present: past perfect + would

If Jim hadn’t missed the plane, he would be here by now.

Colloquial past situations

This is technically “incorrect” but many native speakers say this, perhaps to balance the “have” in each part of the sentence.

If I’d have been there, I would have seen her.

Other Tenses in Conditional Sentences

Going to

Going to can replace will.

If you fall, you’ re going to hurt yourself.

It can also be used to mean “intend to” after if.

If you’re going to make trouble, we’ll call the police.

Present perfect

This can be used to emphasis completion after if.

If you’ve finished, then we’ll go.

It is also possible in both parts of the sentence.

If I’ve told you once, I’ve told you a hundred times!

Doubt and uncertainty

An additional not can be added in formal expressions involving doubt. This emphasises the uncertainty and does not add a negative meaning.

I wouldn’t be surprised if it didn’t rain. (I think it will rain.)

The intonation falls on rain; there is no stress on didn’t.

Should

After if , this makes the possibility of an event seem unlikely.

If you should see Ann, could you ask her to call me?

This implies that I do not expect you to see Ann.

Were to

This also makes an event seem more hypothetical.

If I were to ask you to marry me, what would you say?

Happen to

This emphasises chance possibilities. It is often used with should.

If you happen to see Helen, could you ask her to call me?

If you should happen to be passing, drop in for a cup of tea.

If it were not for / If it hadn’t been for

This describes how one event depends on another.

If it weren’t for Jim, this company would be in a mess.

If it hadn’t been for their goalkeeper, United would have lost.

Will and would : politeness and emphasis

These can be used as polite forms.

If you will/ would wait here. I’ll see if Mrs. Green is free.

Will can also be used for emphasis, meaning “insist on doing”

If you will stay out late, no wonder you are tired! (insist on staying)

Other ways of making a conditional sentence

Supposing, otherwise

Supposing or suppose can replace if, mainly in everyday speech.

Supposing you won the football pools, what would you do?

Otherwise means “or if not”. It can go at the beginning or end of the sentence.

If you hadn’t given us directions, we wouldn’t have found the house.

Thanks for your directions to the house. We wouldn’t have found it otherwise.

But for

This can replace if not. It is used in formal language, and must be followed by a noun form.

If you hadn’t helped us, we would have been in trouble.

But for your help, we would have been in trouble.

If so / If not

These can refer to a sentence understood but not stated.

There is a possibility that Jack will be late. If so, I will take his place.

Colloquial omission of if

An imperative can be used instead of an if clause in everyday speech.      

Sit down, and I’ll make us a cup of tea. (If you sit down . )

If and adjectives

In expressions such as if it is necessary/ possible it is possible to omit the verb be.

If interested, apply within.

If necessary, take a taxi.

Formally if can mean although, usually as if + adjective

The room was well furnished, if a little badly decorated.