情态助动词的意义和用法很详细

1、情态助动词的意义和用法情态助动词可以反映说话者对其表述是否真实和可能的程度作出判断。1） can和could的用法1. 表示能力，如： Can you finish this work tonight?2. 理论上的可能性，但未必马上发生。“有时候会” Man cannot live without air. My sister can be really stubborn.3. 表示请求和允许。 Can I go now? Yes, you can.注意：could也可表示请求，语气委婉，主要用于疑问句，不可用于肯定句，答语应用can（即could不能用于现在时态的简略答语中）。如： Cou

2、ld I come to see you tomorrow? Yes, you can. （否定答语可用No, Im afraid not.）can表示能力时，还可用be able to代替。如： Ill not be able to come this afternoon.4. can表示惊异、怀疑、不相信的态度，是一种推测.（主要用在否定句、疑问句或惊叹句）Could既可用于肯定句又可用于否定句、疑问句Can this be true? How can you be so careless!This cannot be done by him.5. “can + have done” 用于

3、否定句、疑问句表示对过去发生的行为怀疑或不肯定。“could + have done”可用于各种句型。如：He cannot have been to that town.Can he have got the book?6. 特殊句式（1） can not / can never too或cannotenough “再也不过分，越越好” One cant be too careful. = One cant be careful enough.（2）cant help doing / cant help but do禁不住，不由得（3）Cant help (to) do 不能帮助做某事(4)

4、 cant/couldnt + 比较级=最高级2） may和might的用法1. 表示许可。表示请求、允许时，might比may的语气更委婉一些，否定回答时要用mustnt表示“不可以”、“禁止”、“阻止”之意。如：You may drive the car. Might I use your pen? No, you mustnt. 用May I . 征询对方许可在文体上比较正式，在口气上比较客气。在日常口语中，用Can I . 征询对方意见在现代口语中更为常见。肯定回答用Yes, you may./Yes, please./Certainly./Sure, go ahead.否定回答用No

5、, you mustnt./No, youd better not.2. 用于祈使句中表示祝愿。May+主语+动词原形如： May you succeed!3. 表示推测,一般不用于疑问句。might的可能性比may小。 He may be very busy now.4. “may(might) + have done”表示对过去发生的行为的推测。如： He may not have finished the work.5. may / might as well 动词原形 “不妨，不如” You may / might as well go to see a doctor.3） must和

6、have to的用法1. 表示必须、必要。如：You must come in time.回答must引出的问句时，如果是否定的回答，不能用mustnt，而要用neednt或dont have to。 Must we hand in our exercise books today? Yes, you must. (No, you dont have to.)2. must表示命令或强制，用于否定句的mustnt表示说话人不许或禁止（某人做某事）。例如：You must do as you are told 你必须遵嘱行事。 You mustnt move any of the papers

7、on my desk 你不许动我办公桌上的任何文件。 May I borrow this book？ 我可以借这本书吗？ No，you mustnt 不，不可以。3. must表示“偏要”， “非要”Must you make so much noise？ 你偏要弄出那么多噪音吗？Of course，after I gave her advice， she must go and do the opposite 当然，在我劝了她以后，她非要做相反的事不可。4. must表示推测，只用于肯定句。它的否定或疑问式用can/could代替must。 This must be your pen.5.

8、“must + have + done”的结构常用在肯定句中，表示对过去发生的行为的推测。它的否定或疑问式用can/could代替must。He must have been to Shanghai.含Must的反义疑问句：Amust表示“应该”，其疑问部分用mustnt（不应该），如： You must work hard next term, mustnt you ? 下学期你应该努力学习，对吗？ Bmust表示“必须”，其疑问部分用neednt（不必），如： They must finish the work today, neednt they? 他们今天必须要完成这项工作，是吗？C陈

9、述部分含情态动词mustnt，表示禁止时，疑问部分就可以用must或may，如： You mustnt stop your car here, must you? (may we?)你不能把车停在这地方，知道吗？ Dmust表示推测 ，其疑问部分必须与must 后面的主要动词相呼应。如： 对现在动作或存在的情况的推测 ： You must know the answer to the exercise, dont you? 你一定知道这项练习的答案，是不是？ That must be your bed, isnt it? 那一定是你的床，是吗？ 对过去发生的动作或存在的情况的推测： （一）句中

10、陈述部分没有表示过去的时间状语，这时疑问部分中的动词就用现在完成时。（havent / hasnt + 主语）You must have told her about it, havent you? 你一定把这事告诉她了，是吗？（二）陈述部分有表示过去的时间状语，疑问部分的动词就用一般过去时。（didnt + 主语）She must have read the novel last week, didnt she? 她上星期一定读了这本小说了，是吗？6. have to的含义与must相似，两者往往可以互换使用，但have to有各种形式，随have的变化而定。must与have to有下列几

11、点不同： must表示的是说话人的主观看法，而have to则往往强调客观需要。如：The play is not interesting. I really must go now.I had to work when I was your age. 二者的否定意义不大相同。如：You mustnt go. 你可不要去。 You dont have to go. 你不必去。 询问对方的意愿时应用must。如： Must I clean all the room?4） dare和need的用法1. need表示“需要”或“必须”，作情态动词时，仅用于否定句或疑问句中，在肯定句中一般用must,

12、 have to, ought to,或should代替。如：You neednt come so early. Need I finish the work today? Yes, you must.注意：neednt +完成式“表示本来不必做而实际上做了某事”。如：You neednt have waited for me.2. Dare作情态动词时，主要用于疑问句、否定句和条件从句中，一般不用在肯定句中。有过去时dared。如：How dare you say Im unfair.He darent speak English before such a crowd, dare he?3

13、. Dare和need可作实义动词，用于各种句型，有时态、人称和数的变化，所不同的是，作实义动词时，在肯定句中，dare后面通常接带to的不定式，在否定和疑问句中，dare后面可接带to或不带to的不定式。如：I dare to swim across this river. He does not dare (to) answer.Dont you dare (to) touch it! He needs to finish it this evening.5） shall和should的用法Shall（1）用于第一人称的陈述句，表示将来。如：I shall come tomorrow.（2

14、）. Shall用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。如：Shall we begin our lesson?When shall he be able to leave the hospital?（3）. Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。如：You shall fail if you dont work harder. （警告）He shall have the book when I finish reading. （允诺） He shall be punished. （威胁）（4）应该,应当.用于条约，规定，规章等文件中，

15、表示一种义务，多用于第三人称中。He shall have the right to own the house according to the law.（法律条文）-Can I pay the bill by check?-Sorry, sir. But its the management rules of our hotel that payment shall be made in cash.（规章制度）Should （1）表示劝告、建议、命令，其同义词是ought to；在疑问句中，通常用should代替ought to。如：You should go to class right

16、 away.Should I open the window?(2) should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。 I should think it would be better to try it again. 我倒是认为最好再试一试。 You are mistaken, I should say. 依我看，你是搞错了。(3)Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能。相当于“万一”的意思。从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气。如： If you should change your m

17、ind, please let us know. 万一你改变主意，请通知我们。 Should I (If I should) be free tomorrow I will come. 万一我明天有时间，我就来。(4)此外，Why(or How) + should结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会”。如： Why should you be so late today? 你几天怎么来得这么晚？ Where is Betty living? 贝蒂住在哪里？ How should I know? 我怎么会知道呢？ I dont know why you should t

18、hink that I did it. 我真不知道你凭什么认为这事是我干的。(5). Should 表示推测，按常理，按惯例应该. 如。 They should arrive by 10 oclock. “should /ought to+ have done”表示本应该做而实际上没有做，包含一种埋怨、责备的口气。如： She should have finished it. I should have helped her, but I never could.6） will和would的用法1. 表示请求、建议等，“Will/Would you .” would比will委婉客气。如：Wo

19、uld you pass me the book?2. 表示意志、愿望和决心。如：I will never do that again. They asked if we would do that again.3. will表示习惯和倾向性。 will表示现在的习惯，would表示过去的习惯，此时的意义接近used to 如：Oilwillfloatonwater.油总是浮在水上。Thiswindowwontopen.这扇窗户经常打不开。Thewoundwouldnotheal.(过去伤口老不愈合。would与used to的区别：1）used to强调今昔对比（过去这样，现已不是这样）；w

20、ould只是回顾过去,常与often, frequently,sometimes, always, for hours,on Sundays等表频率的词连用。2）would只能表示过去习惯性的动作，而used to 既可表示动作，也可表示状态4. will表示对目前情况的推测，主要用于第二、三人称。如：This will be the book you want.He will have arrived by now.7） ought to的用法1. Ought to表示应该。如：You ought to take care of him.2. 表示推测。注意与must表示推测时的区别：He

21、must be at home by now. （断定他已到家）He ought to be home by now. （不十分肯定）3. “ought to + have done”表示过去应做某事而实际未做。如：You ought to have asked him (but you didnt).这时，ought to和should可以互相换用。8） used to，had better，would rather的用法1. Used to表示过去的习惯动作或状态，现在已不存在，在间接引语中，其形式可不变。如：He told us he used to play football when

22、 he was young.在疑问句、否定句、否定疑问句或强调句中，可有两种形式：疑问句 Did you use to go to the same school as your brother? Used you to go to the same school as your brother?否定句 I usednt to go there. I didnt use to go there.Usednt 亦可拼作usent，但发音皆为ju:znt。否定疑问句 Usent you to be interested in the theatre? Didnt you use to be int

23、erested in the theatre?强调句 I certainly used to smoke, but it was a long time ago. I certainly did use to smoke, but it was a long time ago.其反意疑问句或简略回答中，也有两种形式：She used to be very fat, didnt she? （正式）/ use(d)nt she? （口语）Did you use to play chess? Yes, I did.Used you to get up early in the morning? Ye

24、s, I did. (Yes, I used to.)2. Had better意为“最好”，后接不带to的不定式。如： We had better go now. Yes, we had (wed better / we had better).Hadnt we better stop now? (Had we better not stop now?)I think Id better be going. （用于进行时态，表“最好立即”）You had better have done that. （用于完成时态，表未完成动作）注：had best与had better同意，但较少用You

25、 had better 用于同辈或小辈，对长辈不可用。3. Would rather意为“宁愿”，表选择，后接不带to的不定式。如：Id rather not say anything. Would you rather work on a 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。如：I would rather work on a farm than in a factory.Id rather you didnt talk abou

26、t this to anyone. 9）情态动词+have done（陈述过去）must have done （肯） 定/肯定做过某事may have done （肯，否） 可能做过某事might have done （肯，否） 本能够做某事却未做 可能做过某事can have done （否，疑问） 可能做过某事could have done （肯，否，疑问 本能够做某事却未做 /可能做过某事should / ought to have done 本应该做某事却未做 neednt have done 本没必要做某事却做了 10）情态动词表推测1 表示肯定的猜测时，各情态动词语气强弱如下：最强

27、must（一定）will （很有可能） would（很有可能） ought to（应该，很有可能） should（应该，很有可能）can（可能）could（可能）may（可能）最弱might（可能）2 表示否定的猜测时cant / couldnt语气最强，指“不可能”；may / might not语气最弱，意思是“可能不”。3 一些情态动词表猜测时的用法限制。must只用于肯定句；may/ might一般不用于疑问句；could可用于各种句式；而can多用于否定句、疑问句，用于肯定句时，多指“客观可能性”。Lightning can be very dangerous.闪电可能会非常危险。4

28、. 把握题干猜测语气的强弱。题干中如果有客观依据，应该选择猜测语气最强的情态动词；如果没有客观依据，则应选择猜测语气最弱的情态动词。如： Are you coming to Jeffs party? Im not sure. I _go to the concert instead.A. must B. wouldC. should D.might巩固练习1Is John coming by train? He should，but he _ not. He likes driving his car.A.must B.can C.need D.may2The room is so dirty

29、._ we clean it? Of course.A.Will B.Shall C.Would D.Do3. My English-Chinese dictionary has disappeared.Who _ have taken it? A.should B.must C.could D.would4.I heard they went skiing in the mountains last winter. It _true because there was little snow there.A.may not be B.wont be C.couldnt be D.mustnt

30、 be5. It has been announced that candidates _remain in their seats until all the papers have been collected. A.canB.willC.mayD.shall6.There were already five people in the car but they managed to take me as well. It _ a comfortable journey.A.cant beB.shouldnt be C.mustnt have beenD.couldnt have been

31、7.Did the train arrive in time? No.It _two hours ago.A.must have arriveB.ought to have arrived C.must arriveD.ought to arrive8.I cant find my wallet. You _ it on the bus.A.must forgetB.must leave C.must have forgottenD.must have left9.Such a businessman _ be honest.He gets his money in a dishonest w

32、ay.A.cantB.mustnt be C.may notD.shouldnt10.Peter _ come with us tonight，but he isnt very sure yet.A.must B.may C.can D.will11.The girl used to be very interested in music，_ she?A.didnt B.use C.used D.usednt to12.The old woman _ sit there for hours，recalling her good old days.A.would B.used C.used to

33、 D.could13.My watch is out of order.It needs _.A.repair B.repaired C.repairing D.to repair14.Its seven oclock.Jack _ be here at any moment.A.must B.need C.should D.can15.Its still early.You _ hurry.A.mustnt B.wouldnt C.may not D.dont have to16.Do you think the flight is delayed? It _ be，especially i

34、n such weather.A.would B.should C.might D.ought to17.Tom didnt see her in the meeting room this morning.She _ have spoken at the meeting.A.couldnt B.mustnt C.shouldnt D.neednt18.The light is still on.The student _ to switch it off.A.must forgetB.must have forgotten C.might forgetD.may forget19.You m

35、ust be a writer，_ you? A.cantB.arent C.mustD.mustnt20.You ought _ for what you are unable to do.A.not to be punishedB.to not be punished C.to not punishedD.not be punished21.If you had been more careful enough，you _ have made so many mistakes.A.wont B.mustnt C.shouldnt D.wouldnt22.I hear youve got a

36、 set of valuable Australian coins._ I have a look? Yes，certainly.A.May B.Do C.Shall D.Should23.Do you think I could borrow your dictionary? _.A.Yes，you may borrowB.Yes，you could C.Yes，go on D.Yes，help yourself24.The plant is dead.I _ it more water.A.will giveB.would have given C.must give D.should h

37、ave given25.You _ return my umbrella now.You can keep it till next week if you like.A.cant B.mustnt C.neednt D.may not26.Tom ought not to _ me your secret，but he meant no harm.A.have told B.tell C.be telling D.having told27.He told Sally how to get there，but perhaps he _ out for her.A.had to write i

38、t B.must have written it C.should have written itD.ought to write it28.Johnny，you _ play with the knife; you _ hurt yourself.A.wont; cantB.mustnt; may C.shouldnt; mustD.cant; shouldnt29.Its a fine day.Lets go fishing，_?A.wont we B.will we C.dont we D.shall we30.Be sure to write to us，_ you? A.willB.

39、arent C.can D.mustnt31.Would it bother you if I talk to you for a minute? _.A.Yes，pleaseB.No，I dont C.Yes，please dontD.Not at all32.I _ tell you what he did for fear that he should be angry with me.A.darentB.darent to C.dared not toD.dares not33.I should have put on my coat when we left. Its a pity

40、that you _.A.didnt B.dont C.havent D.hadnt34.Arent you a football player? _.A.Yes，Im notB.Yes，I was C.Oh，I used to beD.Oh，I used be35.If you really want yourself to be healthier，you must _ always _ so much.A.not; be smokingB.not; have smoked C.not; to smokeD.be not; smoking36.A computer _ think for itself.It must be told what to do.A.cant B.couldnt C.may not D.might not37.When can I come for the photos? I need them tomorrow afternoon. They _ be ready by 12:00. A.can B.should C.mightD.need38.I didnt hear the phone.I _ asleep.A.must beB.must have been C.should beD.should have been39.He _ you m