If any etc.
Note also the common rather formal use of if before non assertive words like any, anything, ever and not.
There is little if any good evidence of flying saucers (=there is little evidence, if there is any at all…)
I’m not angry, if anything, I feel a little surprised.
He seldom, if ever, travels aboard.
Usually, if not always, we write cannot as one word.
If so and if not
After if we can use so and not instead of repeating or negating clause that has come before.
Are you free this evening? If so, let’s go out for a meal (=…if you are free…)
I might see you tomorrow, if not, then it will be Saturday.
Giving reasons with if
An if clause can be used when somebody admits a fact and gives a reason for it.
If I am a bit sleepy, it is because I was up all night.
If meaning I’m saying this in case
If-clauses are quite often used to explain the purpose of a framework – to suggest I’m saying this in case…
There is some streak in the fridge if your are hungry.
If you want to go home, Mark has got your car keys.
If – other words with the same meaning
Many words and expressions can be used with a similar meaning to if, and often with similar structures. Some of the common uses are imagine (that), suppose (that), supposing (that), providing (that), provided (that), as/so long as, on condition (that).
Imagine we could all fly, wouldn’t that be fun.
Supposing you fell in love with your boss, what would you do?
You can borrow my bike providing/provided you bring it back.
I will give you the day off on condition that you work on Saturday morning.
You are welcome to stay with us as/so long as you share the expense.
If – meaning ‘although’
In a formal style, if can be used with a similar meaning to although. This is common in structure if + adjective (with no verb). If is not as definite as although; it can suggest that what is being talked about is a matter of opinion, or not very important.
His style, if simple, is pleasant to read.
If I were you
We often use the structure if I were you… to give advice.
If I were you, I’d get that car serviced.
I shouldn’t worry if I were you.
If I was you… is also possible, but it is more informal.
Sometimes we leave out if I were you and just instead use I should… to give advice. (I would is normal American English)
I should get that car serviced.
I shouldn’t worry.
In this case I should means more or less the same as you should.
We can use if only…! to say that we would like things to be different. It means the same as I wish…, but more emphatic. The clause with if only often stands alone without a main clause. We use the same tenses after if only…! Just like after I wish.
Past to talk about the present
If only I knew more people!
If only I was better looking!
We can use were instead of was. This is considered more correct in a formal style.
If only I were better looking!
Would + infinitive to refer to the future.
If only it would stop raining we could go out.
If only somebody would smile!
Past perfect (had + past participle) to refer to the past.
If only she hadn’t told the police, everything would have been all right.