if

I UK [ɪf] / US conjunction ***

1) in a possible or imagined situation

a) used for introducing a situation that may happen or may be real, especially when talking about its results

If we miss the last bus, we'll have to walk home.

If anyone has found a bunch of keys, would they please leave them on my desk.

if you want/like:

You can come and stay with us if you want.

if so (= if this is true):

Are you planning to return to work, and if so, who is going to look after the baby?

if not (= if this is not true):

Has anyone dealt with the technical problems? And if not, why not?

if necessary/if possible (= if it is necessary/possible):

We are ready to fight for our rights if necessary.

I should like to be back here by 10.30 if possible.

b) used for introducing a situation or condition that must exist before something else happens

Okay I'll come with you if you'll promise not to go too fast.

only if:

The rebels say they are ready to stop fighting, but only if the prisoners are released.

c) used for introducing a situation that does not exist now and is unlikely or impossible, especially when talking about its imaginary results

If Luke paid more attention in class, he would achieve better results.

If Freud were alive today, he would approve of our methods.

If you should happen to meet Diane, would you give her a message.

If anyone were to complain, I should merely tell them to write to the manager.

even if:

I'd never sell this painting, even if they offered me a million dollars.

d) used for introducing a situation that might have existed in the past but did not exist, especially when talking about what its results might have been

If I'd known you were coming, I would have had a meal ready for you.

If the new safety system had been in use, the accident would never have happened.

2) used when something is always true used for introducing a situation that always has the same result, meaning, or effect

I always get a headache if I watch too much television.

If you drive without insurance, you're breaking the law.

3) whether

a) used in indirect questions that ask whether something is true

She asked me if I was fond of music.

Can you tell me if they're planning to come?

b) used when talking about something that is not certain

I doubt if anyone will be interested in the programme.

Palmer still hasn't decided if he's going to play in Saturday's match.

4) used when someone may want to know something used for introducing the reason that you think someone may want to know something

There are plenty of taxis if you're in a hurry.

If you really want to know, I'm fed up with this stupid job.

If anyone asks you where I am, I'll be in the library.

5) used for saying how you feel about a possibility

a) used for saying how you feel about the possibility that something may happen or be true

I'm sorry if I've said anything that has caused offence.

I don't care if I never see her again.

b) used when expressing an opinion about an imagined situation

It would be a pity if they had to cancel the show.

Wouldn't it be nice if we could spend more time with the children?

6) spoken used in requests

a) used when politely asking someone to do something or when asking for permission to do something

I would be grateful if you would send me further details of the programme.

if you don't mind/if it's all right with you:

If you don't mind, I'd like to sit at the back.

b) used when politely trying to add something to a conversation or discussion

If I could just make a suggestion – why don't we invite Andrew to our next meeting?

7) although perhaps used for introducing a remark that makes your description seem slightly less positive or certain

The stories are basically true, if a little exaggerated.

Donald's essays are always interesting, if sometimes rather careless.

8) used when an explanation may be needed used for referring to something that someone may have noticed, before explaining the reason for it

If I seem angry sometimes, it's usually because I'm very tired.

9) possibly more, or possibly less used for suggesting that something may possibly be more or less, better or worse etc than you have stated

Fodor's predictions have seldom if ever been proved wrong.

if not:

The changes will affect thousands, if not millions, of ordinary people.

10) spoken used for showing surprise used for introducing a negative expression to emphasize that you think something is very surprising or shocking

Well, if that isn't the stupidest thing I ever heard!

•

if it were not for/if it had not been for — used for saying who or what prevented something from happening

If it hadn't been for the two men who rescued me, I'd probably have drowned.

If it weren't for the fact that he's my father, I'd accuse him in public.

what if...? — used for asking what would happen in a particular situation

What if the boss walked in here now and saw us?

What if we just cancel the whole thing?

- if anything

- if ever

- if I were you

- if only

See:

as

II UK [ɪf] / US noun

it's/that's a big if — used for emphasizing that something is not certain at all

If we move – and that's a big if – I'll have to find a new job.

- ifs and buts