SynonymwhetherDo you know if he's married?I wonder if I should wear a coat or not.He couldn't tell if she was laughing or crying.Listen to the tune and see if you can remember the words.5 used after verbs or adjectives expressing feelingsI am sorry if I disturbed you.I'd be grateful if you would keep it a secret.Do you mind if I turn the TV off?6 used to admit that something is possible, but to say that it is not very importantIf she has any weakness, it is her Italian.So what if he was late. Who cares?7 used before an adjective to introduce a contrastHe's a good driver, if a little over-confident.We'll only do it once— if at all.8 used to ask somebody to listen to your opinionIf you ask me, she's too scared to do it.If you think about it, those children must be at school by now.If you remember, Mary was always fond of animals.9 used before could, may or might to suggest something or to interrupt somebody politelyIf I may make a suggestion, perhaps we could begin a little earlier next week.
if and when
used to say something about an event that may or may not happenIf and when we ever meet again I hope he remembers what I did for him.
used to express an opinion about something, or after a negative statement to suggest that the opposite is trueI'd say he was more like his father, if anything.She's not thin—if anything she's on the plump side.
if I were you
used to give somebody adviceIf I were you I'd start looking for another job.
if not1 used to introduce a different suggestion, after a sentence with ifI'll go if you're going. If not (= if you are not) I'd rather stay at home.2 used after a yes/no question to say what will or should happen if the answer is ‘no’Are you ready? If not, I'm going without you.Do you want that cake? If not, I'll have it.3 used to suggest that something may be even larger, more important, etc. than was first statedThey cost thousands if not millions of pounds to build.
used to say that you wish something was true or that something had happenedIf only I were rich.If only I knew her name.If only he'd remembered to send that letter.If only I had gone by taxi.
it's not as if
used to say that something that is happening is surprisingI'm surprised they've invited me to their wedding—it's not as if I know them well.
Usage note: if / whetherBoth if and whether are used in reporting questions which expect ‘yes’ or ‘no’ as the answer:She asked if/whether I wanted a drink., although whether sounds more natural with particular verbs such as discuss, consider and decide. When a choice is offered between alternatives if or whether can be used:We didn’t know if/whether we should write or phone. In this last type of sentence, whether is usually considered more formal and more suitable for written English.