From Longman Dictionary of Contemporary Englishifif1 /ɪf/ ●●●S1W1 conjunction1IFused when talking about something that might happen or be true, or might have happenedWe’ll stay at home if it rains.If you need money, I can lend you some.If I didn’t apologize, I’d feel guilty.If you had worked harder, you would have passed your exams.What would happen to your family if you were to die in an accident?If Dad were here, he would know what to do.Taste the soup and add salt and pepper if necessary.I want to get back by five o’clock if possible.I think I can fix it tomorrow. If not, you’ll have to wait till Friday.Is the book available, and if so, where?The missiles can be fired only if the operator types in a six-digit code.We’ll face that problem if and when it comes along (=if it happens or when it happens).If by any chance you can’t manage dinner tonight, perhaps we can at least have a drink together.2IFused to mention a fact, situation, or event that someone asks about, or is not certain aboutHe stopped to ask me if I was all right.I don’t know if what I am saying makes any sense.I doubt if anyone will remember me.I’m not sure if this is the right road or not.3IFused to mention a type of event or situation when talking about what happens on occasions of that typeIf I go to bed late, I feel dreadful in the morning.Plastic will melt if it gets too hot.4used when saying what someone’s feelings are about a possible situationYou don’t seem to care if I’m tired.I’m sorry if I upset you.It would be nice if we could spend more time together.5spoken used when making a politerequestI wonder if you could help me.I’d be grateful if you would send me further details.Would you mind if I open a window?If you would just wait for a moment, I’ll try to find your papers.6used when you are adding that something may be even more, less, better, worse etc than you have just saidBrian rarely, if ever, goes to bed before 3 am.Their policies have changed little, if at all, since the last election.Her needs are just as important as yours, if not more so.The snow was now two feet deep, making it difficult, if not impossible, to get the car out.7 →even if8 →if anything9spoken used during a conversation when you are trying to make a suggestion, change the subject, or interrupt someone elseIf I might just make a suggestion, I think that the matter could be easily settled with a little practical demonstration.If I could just take one example to illustrate this.10 →if I were you11 →if only12used to say that, although something may be true, it is not importantIf he has a fault at all, it is that he is too generous.Her only problem, if you can call it a problem, is that she expects to be successful all the time.13ALTHOUGHused when adding one criticism of a person or thing that you generally likeThe eldest son was highly intelligent, if somewhat lazy.Lunch was a grand if rather noisy affair. → as ifat as2(9), → if ever there was oneat ever(15), → what if ... ?at whatGrammarChoosing the right tense• You use if with the present tense, when talking about possible future events: If I see him, I’ll tell him.✗Don’t say: If I will see him, I’ll tell him.• You use if with the past tense to talk about something that is unlikely or impossible: If I won the lottery, I would leave my job.✗Don’t say: If I would win the lottery ...• In everyday spoken English, you say if I was: If I was younger, I’d do it myself.• In more formal English, you say if I were: If I were in your position, I’d ask for help.• You use if with the past perfect to talk about something that did not happen: If they had tried to stop the protest, there would have been a riot. ✗Don’t say: If they would have tried to stop the protest ...• You also use if with the present perfect, when talking about whether something has happened or not: If she hasn’t called by tomorrow, I’ll call her.Comparisonif• You say: I’m not sure if I heard him correctly.I don’t know if he is guilty.whether• You say: I’m not sure whether I heard him correctly.I don’t know whether he is guilty.• You can use whether after a preposition: We discussed the issue of whether to pay.✗Don’t say: the issue of if to pay• You can say whether to do something: He doesn’t know whether to accept.✗Don’t say: He doesn’t know if to accept.THESAURUSif used when talking about the possibility that something might happen or be trueHe faces a long prison sentence if the court finds him guilty.If scientists’ predictions are correct, average global temperatures could rise by 6 degrees.unless if something does not happen, or if someone does not do somethingThe star is difficult to see unless the sky is very clear.Doctors said they could not treat the boy unless his parents gave their permission.whether or not used when saying that it does not matter if something happens or not, or if something is true or notMost people will get better on their own, whether or not they receive medical treatment.I’m still going, whether she likes it or not.otherwise used when saying that there will be a bad result if someone does not do something, or if something does not happenDrink plenty of water – otherwise you will become dehydrated.in case in order to deal with something that might happenShe did not think it would rain, but she took her umbrella just in case.It is best to keep a medical kit ready in case of emergency.as long as/provided that only if something else happens or is trueVisitors are welcome, as long as they bring their own tent.Anyone can join the course, provided that there is space available. As long as you can find a computer, you can access an internet-based bank account wherever you are.on condition that used when you agree to do something only if someone first agrees to do something elseHe was offered the job on condition that he went on a month-long training course.