8.情态动词.doc

语法专项（八）情态动词一情态动词的含义： 情态动词只有情态意义，即表示说话人对动作的观点，如需要，可能，意愿或怀疑等。情态动词主要有：can(could), may(might), must, shall(should), will(would), need, dare(dared), have to(had to),ought to, had better，would rather, used to等。二情态动词的特征：1在形式上，情态动词没有实义动词的各种变化，只有could, would, had to, might, should等几个过去式。其他如must, ought to等的过去式皆与现在式同形，且在各种人称后都用同样的形式。2在意义上，大多数情态动词有多个意义。如can可表示“能够”，“可能”，“允许”等。3在用法上。情态动词（除ought后接不定式外）与助动词一样，后接动词原形构成谓语动词。三情态动词的用法：（一）can/could的用法：1表示能力：表示现在的能力用can；表示过去的一般能力用could，若表示过去经过努力而做成某事，则用was/were able to do sth. 或managed to do sth. 或succeeded in doing sth.-Everyone here can speak English. (现在的能力)-A fire broke out in the hotel last night, but everyone was able to escape. (经过努力做成某事)表示将来的能力常不用can,而用will be able to的将来时态：-Ill be able to speak French in another few months.2表示请求许可：若表示请求别人允许自己做某事，can/could均可，could表示委婉语气。若表示自己允许别人做某事一般只用can：-Could/Can I use your pen? -Yes, of course you can. (此时一般不用could)3表示推测：can可用于肯定句中表推测，表示理论上的可能性，只有一种时态：can do sth，可翻译为“有时会”。Even experienced teachers can make mistakes.It can be very cold here in May.could在肯定句中表推测，译为“可能”，可以有对过去、现在和将来三个时态的推测，could比can的可能性小。对过去的推测在could后接动词的完成式，即“could have done”。He could have gone home.（过去）He could be doing his homework.（现在的动作）He could be at home.（现在的状态）It could rain tomorrow.（将来）can通常都用于否定句或疑问句，cant和couldnt一样，可以有对过去、现在和将来三个时态的推测，译为“不可能，一定不”，是对must的否定。Can this be true?It cant/couldnt rain tomorrow.（将来）This book cant/couldnt belong to him. （现在的状态）He cant/couldnt be playing football.（现在的动作）He cant/couldnt have seen her there.（过去）could have done可以表示过去本能够发生却没发生的事情，意为“本能够”（虚拟），couldnt have done译为“本不能够”。We could have gone there on foot. A taxi wasnt necessary at all.If it had not been for her help, we couldnt have finished the work ahead of time.4.一些惯用法。 can not/nevertoo/enough/more表示“无论怎么也不过分”，“越越好”，如： You cannot be too careful. You cannot remember enough English words. cannot but do sth 表示“不得不，只好” I could not but choose to go. I cannot but admire his courage. can but do sth. 只好，不得不 We can but agree with him. cannot (couldnt) help doing sth.= cannot help but do sth. 情不自禁做某事。如： When I heard what the little girl said I couldnt help laughing.（二）may/might的用法：1表示许可：若表示请求别人允许自己做某事，may/might均可，若表示自己允许别人做某事一般只用may：-May/Might I sit here? -Yes, you may. (此时一般不用might)2表示推测：表示说话人的猜测，认为某事或许，可能发生，在肯定句中同could的用法，译为“可能”，may比could的可能性小，might比may的可能性小; may一般不用于疑问句表推测，但可用于肯定句和否定句，在否定句中may not/might not译为“可能不”，是对could/may/might的否定He may/might be sick. He may/might have gone to have his hair cut. She may/might not like this place. 注意may not/might not和cant/couldnt区别： may not/might not “可能不” -It may not be true. 这可能不是真的。 can not /could not “不可能” -It can not be true. 这不可能是真的。might have done可表示过去可能发生而实际上并未发生的事情，意为“本可能”（虚拟），might not have done译为“本不可能”It was really very dangerous. I might have killed myself. 那真是太危险了，我差点没命了。3表示祝愿：“May+主语+动词原形”= wish sb adj./n./to do sth-May all your dreams come true! 愿你梦想成真！-May God bless you! 愿上帝保佑你！4一些惯用法。may/might (just) as well do不妨，最好; might as well还可用于指过去的情况或比较不愉快的情况。Since its a fine day, we may/might as well walk.The holiday isnt interesting. We might as well be back home. may well do sth 是一种常用结构，意为 “完全能，很可能”，相当于 to be very likely to ,如： He may well be proud of his son. Her appearance has changed so much that you may well not recognize her. may/might as well do sth as do sth. 与其不如；最好不要。如： You might as well throw your money away as lend it to him.（三）shall/should/ought to的用法：1shall的用法： 第一人称的陈述句：相当于will一三人称的疑问句：表示征求对方意见。 二三人称的陈述句：表示说话者的允诺，告诫，威胁，命令，规定，必然性等。主语是表示规章，法令，预言等，可译为“必须”-Shall the boy come at once? (征求意见)-You shall suffer for this. 你会为此吃苦头的。(威胁)-Tell him that he shall have the book tomorrow. (允诺)-Persons under 18 shall not be employed in night work. (规定) -The law of Venice says that if anyone tries to kill or murder any citizen of Venice, everything that he owns shall be taken away from him.(法令)2should的用法：表示义务，责任，建议或劝告，译为“应该”-We should learn from each other.-You should give up smoking.表示推断：should表示推断时语气较肯定，常指非常有可能的事（有一定的事实依据或合乎常理），译为“按道理应该”-When can I come for the photos? I need them tomorrow afternoon.-They should be ready by 12:00. (1998年高考题)表示意外或惊讶，意为“竟然”，有时与why, who, how等疑问词连用，意为“怎么会”：-Its strange that he should come so late. 他竟然来这么迟真是奇怪。-How should I know? 我怎么会知道？表示谦逊或委婉：常与like, love, think, say, imagine连用：-I should like to know why. 我想知道这是为什么。-I should imagine it will take about three hours. 我想得花大约三个小时。should have done还可表示过去本应该发生却未发生的事情，意为“本应该”(虚拟)，shouldnt have done译为“本不应该”You should not have left so soon. 你本不该那么早走的。3ought to的用法：ought to可表示义务，责任，建议，劝告，推断等，此时可与should互换，语气比should强。ought to have done “本应该”（虚拟），oughtnt to have done“本不应该”（同should和shouldnt）否定句中用ought not或oughtnt，在疑问句中将ought提到主语前：He ought to go now, oughtnt he?Ought I to go? 在美国英语中，ought to用于否定句和疑问句时可将to省略（肯定句to不宜省）；另外，在省略句中也可以省to：Ought we (to) have done it? 我们本该做此事吗？Ought I to go? Yes, you ought（to）. “我该去吗？”“对，你该去。”（四）will/would/used to的用法：1will/would:表示意愿（一般情况下will表示现在的意愿，would表示过去的意愿，但would也可用于表示现在的意愿，语气较委婉）He wouldnt help me yesterday. I would go there with you.If you will allow me, I will see you home. 如果你愿意，我可以送你回家。主要用于第二人称的疑问句中，will和would均可用，would此时并不表示过去，而表示委婉语气。Wont you take off your coat?Would Sunday night suit you? Will you/ Would you like？表示肯定含义的请求劝说时，疑问句中一般用some，而不是any.Would you like some cake?would有时用于提出想法，通常与like, love, hate, prefer, be glad, be happy等连用，若用于第一人称有时也可将would换成should：I should like/ love to have a look at it.I would prefer not go out today.will可表示说话者临时做出的决定：-Mike, the phone is ringing. Do you want me to go? -No, sit still. I will get it.表示习惯和倾向性，比较客观的将来Oil will float on water. 油总是浮在水面上。The window wont open. 这扇窗户经常打不开。The wound would not heal. （当时）这伤口老不愈合。Dont get that ink on your skirt, for it wont wash out.2. would/used to: “过去常常”would 表示过去常常做某事，现在不知道做不做；used to 表示过去常常做某事，现在已经不做了。Every evening he would tell a story to us.There used to be an old temple here.若强调过去与现在的对比，只用used to:He is not what he used to be. 他已经不是从前的他了。I dont smoke these days, but I used to. used to的否定式和疑问式：I usednt/didnt use to smoke.Used you/Did you use to be very thin?There used to be a lake in the park, usednt there/didnt there?（五）must/have to的用法：1must的用法：表示“必须”“一定要”（否定句中表示绝对禁止“不要” “一定不能”；表示“不必”用neednt）You must finish your homework today.We mustnt think only of ourselves. 我们不能只考虑自己。-Must I come tonight? -No, you neednt.表示推测：只用于肯定句，可以有对过去和现在两个时态的推测，译为“一定”，否定或疑问句用cant/couldnt代替。must do 表示对现在情况的推测must be doing/have been doing 表示对正在发生的事情的推测must have done表示在过去发生事情的肯定推测：He must be wrong（现在的状态）He must be writing a letter to his girlfriend.（现在的动作）I didnt hear the phone. I must have been asleep.（过去）表示不巧或固执，常指令人不愉快的事情，意为“偏偏”“非得”Must you make so much noise? 你非得弄出这么大声音吗？We were ready to leave, but the baby must catch cold. 我们刚准备好要走，可孩子偏偏得了感冒。（表示主张）意为：一定要，坚持要。If you must go, at least wait until the storm is over.有时可以作名词，意为“必须做，看，听等的事情或必须的东西”Greens new novel is a must for all lovers of crime fiction. 格林新出版的小说是爱好犯罪小说者所必看的一本书。A good knowledge of English is a must in international trade.2must与have to 的区别： must: 侧重说话者的主观看法，认为有必要，有义务做某事 have to: 侧重客观需要，含有“不得不”“被迫”的意思You must do what I tell you. (主观)I am afraid you will have to do this; its a rule of the college. (客观) mustnt：意为“不能”dont have to：意为“不必”= neednt = dont need toYou mustnt tell him about it. 你一定不要告诉他这件事。You dont have to tell him about it. 你不必告诉他这件事。（六）need的用法：1既可作实义动词又可作情态动词，意为“需要”。作情态动词时只用于否定句，疑问句以及if/whether之后，一般不用于肯定句。You neednt worry. = You dont need/have to worry.-Need he stay here? -Yes, he must (have to). / No, he neednt/dont have to.-Does he need to stay here? -Yes, he does. / No, he doesnt.2neednt have done可表示过去本不必做某事而实际做了的情况，译为“本不必”（虚拟）You neednt have come in person. 你本不需要亲自来的。3There is no need (for sb) to do sth.（七）dare的用法：1既可作实义动词又可作情态动词，意为“敢”。作情态动词时只用于否定句，疑问句以及if/whether之后，一般不用于肯定句， 过去式为dared：Dare you tell her the truth?I dont know whether he dare try.2用作实义动词时，可以用于各种句型，后接不定式to doDo you dare to tell her the truth?We dont dare (to) say anything.3I dare say “很可能”“大概”I dare say that you are right. 很可能你是对的。（八）had better的用法：意为 “最好”“应该”, had常缩略为d ；有时还可用had bestYoud better go to bed early.You had best get home before midnight.否定式：had better not；疑问式：had sb. betterYoud better not disturb. What had we better do? would rather的用法would rather 意为“宁愿”，表选择，后接不带to的不定式。例如：Id rather not say anything.Would you rather work on farm?-Wouldnt you rather stay here?- No, I would not. Id rather go there.由于would rather表选择，因而后可接than，表示与其不如would rather do sth than do sth = would do sth rather than do sth. 例如：I would rather work on a farm than in a factory.I would watch TV rather than go to see the film.would rather 后接从句，表示虚拟，有两种时态，对现在和将来的虚拟，从句中用一般过去时；对过去的虚拟，从句中用过去完成时。Id rather you didnt talk about this to anyone.I would rather you hadnt done that.四情态动词的注意点（一）情态动词+ have done1表示对过去情况的推测：must/could/may/might/cant/couldnt/may not/might not2表示对过去情况的虚拟：could/couldnt /would/wouldnt /might/might not /should/shouldnt /ought to/oughtnt to /neednt3表未曾实现的句式：was/ were to have done 过去本打算/本想would/should like/love to have done 过去本想而没= would/should have liked/loved to do.= had intended to do= intended to have donehad better have done当初最好would rather have done 当初真该My teacher was to have come here last night, but he had an important meeting to attend.I would love to have gone to Beijing that day, but the tickets were sold out.We had better have bought the book.My brother would rather have stayed at home than go to see the dull film.（二）情态动词在反意疑问句中的用法：1“肯定祈使句+附加问句”结构，附加问句常用will/would/ wont you形式。Stand still, will/ would/ wont you?2“否定祈使句+附加问句”结构，附加问句常用will/would you形式Dont watch TV, will/ would you?3Lets ，shall we? Let us ，will you?4含有must句子的反意问句1）must表示“必须”时，附加部分常用neednt，也可用mustnt.He must go with you, neednt/mustnt he?2）must表“一定、想必”推测意时，附加部分主要有下列几种形式：现在的状态He must be an engineer, isnt he? She must have a car/ live there, doesnt she?现在的动作They must be writing now, arent they?过去He must have seen the film, hasnt he? （句子无具体过去时间状语。）He must have seen the film last week, didnt he?（句子有具体过去时间状语）Mother must have been shopping then, wasnt she?（句子的时间状语是then）巩固练习：1. Just be patient. You _ expect the world to change so soon. (2010 全国卷)A. cant B. neednt C. may not D. will not2. -I havent got the reference book yet, but Ill have a test on the subject next month. -Dont worry. You _ have it by Friday. (2010 江苏卷) A. could B. shall C. must D. may3. Doctors say that exercise is important for health, but it _ be regular exercise. (2010 辽宁卷) A. can B. will C. must D. may4. “You _ have a wrong number,” she said. “Theres no one of that name here.” (2010 浙江卷) A. need B. can C. must D. would5. Jack described his father, who _ a brave boy many years ago, as a strong-willed man. (2010 安徽卷) A. would be B. would have been C. must be D. must have been6. -Good morning. Ive got an appointment with Miss Smith in the Personnel Department. -Ah, good morning. You _ be Mrs. Peters. (2010 北京卷) A. might B. must C. would D. can7. You _ buy a gift, but you can if you want to. (2010湖南卷) A. must B. mustnt C. have to D. dont have to8. -May I take the book out of the reading room? -No, you _. You read it in here. (2010 陕西卷) A. mightnt B. wont C. neednt D. mustnt9. Im afraid Mr. Harding _ see you now. Hes busy. (2010全国卷二) A. cant B. mustnt C. shouldnt D. neednt10. You _ park here! Its an emergency exit. (2010 重庆卷) A. wouldnt B. neednt C. couldnt D. mustnt11. I have told you the truth. _ I keep repeating it? (2010 江西卷) A. Must B. Can C. May D. Will12. -_ I take the book out? -Im afraid not. (2010四川卷) A. Will B. May C. Must D. Need13. What do you mean, there are only ten tickets? There _ be twelve. (2009 全国卷一) A. should B. would C. will D. shall14. I cant leave. She told me that I _ stay here until she comes back. (2009 全国卷二) A. can B. must C. will D. may15. One of the few things you _ say about English people with certainty is that they talk a lot about the weather. (2009 北京卷) A. need B. must C. should D. can16. -Hi, Tom. Any idea where Jane is? -She _ in the classroom. I saw her there just now. (2009 重庆卷) A. shall be B. should have been C. must be D. might have been17. The traffic is heavy this day, I _ arrive a bit late, so could you save me a place? (2009 辽宁卷) A. can B. must C. need D. might18. -Its the office! So you _ know eating is not allowed here. -Oh, sorry. (2009湖南卷) A. must B. will C. may D. need19. Some people who dont like to talk much are not necessarily shy; they _ just be quiet people. (2009 安徽卷) A. must B. may C. should D. would20. -I dont care what people think. -Well, you _. (2009 四川卷) A. could B. would C. should D. might21. Liza _ well not want to go on the trip-she hates travelling. (2008 全国卷二) A. will B. can C. must D. may22. John promised his doctor he _ not smoke, and he has never smoked ever since. (2008 北京卷) A. might B. should C. could D. would23. She _ have left school, for her bike is still there. (2008 天津卷) A. cant B. wouldnt C. shouldnt D. neednt24. You dont have to know the name of the author to find a book. You _ find the book by the title. (2008 湖南) A. must B. need C. can D. would25. -What sort of house do you want to have? Something big? -Well, it _ be big-thats not important. (2008 陕西卷) A. mustnt B. neednt C. cant D. wont26. Although this _ sound like a simple task, great care is needed. (2008 四川卷) A. must B. may C. shall D. should27. -I cant find my purse anywhere. -You _ have lost it while shopping. (2008 重庆卷) A. may B. can C. should D. would28. You _ be hungry already-you had lunch only two hours ago! (2008 浙江卷) A. wouldnt B. cant C. mustnt D. neednt29. It is usually warm in my hometown in March, but it _ be rather cold sometimes. (2008 福建卷) A. must B. can C. should D. would30. Peter _ be really difficult at times even though hes a nice person in general. (2008 辽宁卷) A. shall B. shou