if

From Longman Dictionary of Contemporary Englishifif1 /ɪf/ S1 W1 conjunction 1 IFused when talking about something that might happen or be true, or might have happened We’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. 2 IFused to mention a fact, situation, or event that someone asks about, or is not certain about He 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. 3 IFused to mention a type of event or situation when talking about what happens on occasions of that type If I go to bed late, I feel dreadful in the morning. Plastic will melt if it gets too hot.4 used when saying what someone’s feelings are about a possible situation You 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. 5 spoken used when making a polite request I 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.6 used when you are adding that something may be even more, less, better, worse etc than you have just said Brian 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 anything9 spoken used during a conversation when you are trying to make a suggestion, change the subject, or interrupt someone else If 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 only12 used to say that, although something may be true, it is not important If 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. 13 ALTHOUGHused when adding one criticism of a person or thing that you generally like The eldest son was highly intelligent, if somewhat lazy. Lunch was a grand if rather noisy affair. → as if, → if ever there was one, → what if ... ?GrammarChoosing 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. Examples from the Corpusif• It's a really fast car, if a little expensive.• If I drink too much coffee, I have to run to the bathroom all day long.• Do you think I'd be here if I had a choice?• The plastic will melt if it gets too hot.• We'll have to leave Monday if it snows today.• I wonder if Matt's home yet.• I don't care if my boss fires me - I'm still going to tell him what I think.• We're prepared to work all through the night if necessary.• Use live natural yoghurt, full-fat if possible.• If she does well in her exams, she will be going to college in October.• I believe you sell video cameras. If so, please would you send me a price list?• If taken in small doses, the drug has no harmful effects.• Do you know if we have to work on Christmas Eve?• If you call Ann now, she should still be home.• If you do that again I'll hit you.• I'll give you twenty pounds if you fix my computer for me.• I know I look tired. So would you if you had this house, a husband, and three children to look after.• I have a drill. If you like, you can borrow it. if necessary• Add a little extra flour if necessary. 3.• Adjust seasoning with salt, pepper and lemon juice if necessary.• Extracts can be shown, without the sound commentary if necessary.• Eye and ear protection can be supplied if necessary.• Half-pay was to be granted to disbanded officers, to enable them to be recalled if necessary.• I wanted people to think I'd gone to Summertown and I could prove it if necessary.• Sprinkle with remaining herbs, if necessary, and serve at once.• Yes, leave the door slightly open to ensure that if necessary he could leave at speed.• He said that if necessary he would use his presidential veto.if ... or not• He stared at me, but I did not know if he understood or not. ifif2 noun [countable] informal 1 → ifs and buts2 → and it’s a big if3 something that may or may not happen There are too many ifs in this plan of yours.Examples from the Corpusif• There are still too many ifs to know if our product will be successful.IfIf a famous poem by Rudyard Kipling which starts with the words If you can keep your head when all about you/Are losing theirs and blaming it on you... It describes the qualities of character that some people think of as typically English, such as the ability to remain calm in difficult situations.Origin if1 Old English gif

单词	if
释义	if From Longman Dictionary of Contemporary Englishifif1 /ɪf/ ●●● S1 W1 conjunction 1 IFused when talking about something that might happen or be true, or might have happened We’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. 2 IFused to mention a fact, situation, or event that someone asks about, or is not certain about He 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. 3 IFused to mention a type of event or situation when talking about what happens on occasions of that type If I go to bed late, I feel dreadful in the morning. Plastic will melt if it gets too hot.4 used when saying what someone’s feelings are about a possible situation You 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. 5 spoken used when making a polite request I 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.6 used when you are adding that something may be even more, less, better, worse etc than you have just said Brian 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 anything9 spoken used during a conversation when you are trying to make a suggestion, change the subject, or interrupt someone else If 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 only12 used to say that, although something may be true, it is not important If 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. 13 ALTHOUGHused when adding one criticism of a person or thing that you generally like The eldest son was highly intelligent, if somewhat lazy. Lunch was a grand if rather noisy affair. → as if, → if ever there was one, → what if ... ?GrammarChoosing 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. Examples from the Corpusif• It's a really fast car, if a little expensive.• If I drink too much coffee, I have to run to the bathroom all day long.• Do you think I'd be here if I had a choice?• The plastic will melt if it gets too hot.• We'll have to leave Monday if it snows today.• I wonder if Matt's home yet.• I don't care if my boss fires me - I'm still going to tell him what I think.• We're prepared to work all through the night if necessary.• Use live natural yoghurt, full-fat if possible.• If she does well in her exams, she will be going to college in October.• I believe you sell video cameras. If so, please would you send me a price list?• If taken in small doses, the drug has no harmful effects.• Do you know if we have to work on Christmas Eve?• If you call Ann now, she should still be home.• If you do that again I'll hit you.• I'll give you twenty pounds if you fix my computer for me.• I know I look tired. So would you if you had this house, a husband, and three children to look after.• I have a drill. If you like, you can borrow it. if necessary• Add a little extra flour if necessary. 3.• Adjust seasoning with salt, pepper and lemon juice if necessary.• Extracts can be shown, without the sound commentary if necessary.• Eye and ear protection can be supplied if necessary.• Half-pay was to be granted to disbanded officers, to enable them to be recalled if necessary.• I wanted people to think I'd gone to Summertown and I could prove it if necessary.• Sprinkle with remaining herbs, if necessary, and serve at once.• Yes, leave the door slightly open to ensure that if necessary he could leave at speed.• He said that if necessary he would use his presidential veto.if ... or not• He stared at me, but I did not know if he understood or not. ifif2 noun [countable] informal 1 → ifs and buts2 → and it’s a big if3 something that may or may not happen There are too many ifs in this plan of yours.Examples from the Corpusif• There are still too many ifs to know if our product will be successful.IfIf a famous poem by Rudyard Kipling which starts with the words If you can keep your head when all about you/Are losing theirs and blaming it on you... It describes the qualities of character that some people think of as typically English, such as the ability to remain calm in difficult situations.Origin if1 Old English gif
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