情態(tài)動詞的用法在英語中，情態(tài)動詞屬于助動詞。除了作簡略回答外，它們一般不能單獨使用，它們必須與動詞原形一起使用構(gòu)成句子的謂語。不同的情態(tài)動詞會有不同的意義和用法。有時，同一個情態(tài)動詞在不同的語境中也會產(chǎn)生不同的含義。情態(tài)動詞的推測性用法和非推測性用法情態(tài)動詞一般有兩種用法：推測性用法和非推測性用法 。推測性用法是指做出推測,預(yù)測事物發(fā)生的可能性; 非推測性用法則指情態(tài)動詞本身的基本含義，如can表示能力，may表示許可，must和should表示必須和義務(wù)，need表示需要等。例如： I can swim. (非推測性用法) This can be true. (推測性用法) You may go now. (非推測性用法) He may be ill now. (推測性用法) You must finish it before lunch time. (非推測性用法) He must be at home for he never goes out at dinner time. (推測性用法) 我們把英語中的9大情態(tài)動詞按其推測性和非推測性用法列表如下:情 態(tài) 動 詞 非 推 測 性 用 法 推測性用法 cancould 能力/許可(abilitypermission) 可能(possibility) maymight 許可(permission) 可能(possibility) willwould 意愿(volition) 預(yù)言性(predictability) shouldought to責(zé)任和義務(wù)(obligation) 應(yīng)該是(logical necessity) must責(zé)任和義務(wù)(obligation) 一定,肯定(logical necessity) 情態(tài)動詞非推測性用法的說明1. may和might表示允許may可以與不同的人稱搭配，表示“許可、允許”。例如： May I know your name?You may be the first to leave if you are in a hurry. (我允許你第一個離開。) You may keep the book for two months. (我允許你借。) In certain circumstances a police officer may ask a driver to take a breath test.may用在疑問句中，經(jīng)常表示“允許、許可”的意思。例如： May I know your name? May I come in?might可以用來表示過去時態(tài)，也可以表示委婉語氣。例如: She said that he might take her dictionary. (may的過去式) Might I have a word with you? (委婉用法) I wonder if I might have more salad. (委婉用法) 但在回答中，我們一般用may加強肯定的語氣，而不用might.例如：Yes, of course you may.may not可用來表示“禁止”或“不許”，因語氣較強，所以不用might not.例如：Students may not stay out of the dormitory after midnight without written permission.must not也可以表示“禁止”，而且語氣比may not更強，強調(diào)上級對下級的不允許。另外，may/might as well也是一個常用的詞組，后接動詞原形，意思是“不妨，最好”相當于had better.例如：Its very late. We might as well go home.2. can和could1) 表示能力can,could和be able to都可以表示能力。但若要表示在過去某個具體場合下能夠做某事的能力，我們用was/were able to. 例如： Thank you for your help. Im glad I was able to help you. (在這種情況下能夠幫你，而且已經(jīng)幫了。) 所以was/were able to不僅表示過去的某個具體場合下的能力，還強調(diào)動作已經(jīng)成功完成，相當于manage to do或succeed in doing.例如：We were able to save him. (把他救活了。) He was able to explain what had happened. (他能解釋，而且也解釋了。) He could explain what had happened. (他能做出解釋，但可能沒有說。) 但這種區(qū)別只局限在陳述句，在否定句中，be able to和could可以互換。有時，could表示的并不是can的過去式，而是一種委婉的語氣。例如：Could you run the business yourself? Could you please give me your reply as soon as possible?could have done有虛擬的含義，即“本來能夠做，但事實上卻沒有做”。例如：You could have told me earlier. I could have passed the exam if I had worked harder.2) 表示許可can也可以用來表示“允許”，例如： Can I smoke here? The policeman says we cant park our car here.could可以使句子更顯禮貌，但在肯定回答中，我們一般用can代替could,加強肯定的語氣。即：Yes, of course you can. 3) 其他用法can not與help, bear, stand等動詞連用，表示“禁不住，受不了”。例如：If one had talent, one cant help showing it. I cant stand waiting any longer.但是cant help but 后面接動詞原形，表示“只能”。I can not help but ask you: “do you have loved me?” I cant help but wait.3. must表示必須must的這種用法，體現(xiàn)了說話者的權(quán)威性，所以must通常用于上級對下級、長輩對小輩。例如: You must be back by ten oclock. Teacher: You must use a dictionary. Im tired of your spelling mistakes.注意 must和have to的區(qū)別： must表示出于說話者本人的主觀愿望，必須去做某事；而have to表示受外部條件的影響，不得不做某事。例如：I must leave now. (我自己想離開，主觀愿望。) I have to leave now. (也許我還想坐一會兒，但我有要事，不得不走了。) He must say it in English. (除了英語，他可能還懂其他語言，但我的主觀愿望是他必須說英語。) He has to say it in English. (客觀條件是他只懂英語，所以不得不用英語說。) 另外，由于must沒有將來時態(tài)，所以我們通常用willshall have to來表示；由于must沒有過去時態(tài)，所以我們通常用had to來表示。例如：We will have to do it again.I had to leave at 6:30 yesterday.但有時，我們也可以在表示過去的上下文中使用must.例如：I told him that he must mind his own business.must有兩種否定形式： mustnt和needntdont have to. mustnt表示 不可以“，needntdont have to表示“不必”，例如： You mustnt talk like that. (不可以 = You are not allowed to talk like that.) Must you leave so soon? No, I neednt.4. should和ought to should和ought to通?？梢越换ナ褂?，意義沒有多大的區(qū)別，表示“應(yīng)該”。should和ought to的這種用法通常表示“建議、敦促或慫恿”。比較 must, have to和shouldought to所表示的不同語氣： 鋼琴老師對某學(xué)生說：You must practice at least an hour a day. (must 顯示了老師的權(quán)威。) 這個學(xué)生然后對他的朋友說：I have to practice an hour a day! (have to表示我本身不想練，但迫于老師的壓力，不得不練。) 他的朋友會說： You ought toshould practice for more than an hour. (表示不是來自外界的權(quán)威或壓力，而是來自平輩同學(xué)或朋友的建議：如要做個好學(xué)生，彈好鋼琴。) 另外，should have doneought to have done表示“本該發(fā)生的事沒有發(fā)生；例如： You should have told me earlier. You ought to have been more careful.5. will和wouldwill和would作情態(tài)動詞使用，主要有以下的用法： 1) 表示意愿will和would表示的意愿可強可弱，意愿弱時表示“愿意做某事”(willingness) ;意愿強時表示“堅持要做某事”(insistence) .例如： Will you go with us?(愿意) Will you pass me the salt? (愿意) Let us have a talk, will you? (愿意) I will marry her although my parents are strongly against our marriage.(表示堅持) would可以表示“過去的愿意”， 一般用于間接引語中，例如:He said he would come.在其他情況下，would不表示過去，而表示委婉的語氣“，例如： Would you please make a copy for me?但在回答中，為了加強肯定的語氣，我們用will.例如Would you let me hear from you soon? Yes, I will.2) 表示能力、趨勢或必然性will和would的這種用法一般以東西作為主語，表示“其內(nèi)在的性能或特征性傾向”。 例如： Oil will float on water. Gold wont dissolve in acid.否定形式wont還可以表示“某事沒有達到我們期望的效果”。 例如： The car wont start. The door wont open.注意這里用主動語態(tài)。3) 表示習(xí)慣性的動作。例如:Every morning he will sit in the office doing nothing.He will often say something and then forget it.在這種用法中，would是will的過去式。例如： He would never let anybody know what he was doing. In those days he would work day and night, with no time to care for his children.6. shallshall通常有以下用法：1) 表示“說話者的決心或承諾”。 例如： I shall never give up. The invaders shall be wiped out. You shall get your salary tomorrow. (I promise.) He shall get his share. (I promise.) You shall stay with us as long as you like. (I promise.) 2) 表示“命令”，語氣很強。例如： You shall go at once.You shall do as I say.You shall never tell lies.此種語氣因太專橫，所以一般不用，但在法律文件和合同條款中，我們通常用shall 表示權(quán)利和義務(wù)。3) 疑問句中用來征求意見。例如： Shall I pick you up at six? (Do you want me to pick you up at six?) Shall we go together? Lets have a rest, shall we?Shall he go on an errand? (Do you want him to go on an errand?) 7.needneed可以作行為動詞，也可以作情態(tài)動詞。need作行為動詞時，有時態(tài)的變化，后面跟動詞不定式或名詞，其否定式和疑問式要用助動詞；need作情態(tài)動詞時，后面只跟動詞原形，其否定式和疑問式不用助動詞，而是直接在need后面加上not構(gòu)成否定式，疑問句直接把 need提前。 例如： You neednt come. (情態(tài)動詞) I wonder if we need take sleeping bags. (情態(tài)動詞) I need your help. (行為動詞) I need to have a look. (行為動詞) Need we work today? (情態(tài)動詞) Yes, we must. (No, we neednt.) need作情態(tài)動詞，表示“需要”，常用在否定句、疑問句或if引導(dǎo)的從句中，在回答need引導(dǎo)的問句中，肯定回答用must加強語氣，表示“必須”； 否定回答用neednt, 表示“不必”， 相當于not have to.Neednt have done表示“沒有做某事的必要，該事本不必做，但卻做了”； dont need to只是表示“不必做某事，而且該事也確實沒有做”。例如：I didnt need to go to the station.(沒有去車站) I neednt have gone to the station. (去了車站) 8. daredare可以作行為動詞，也可以作情態(tài)動詞。dare作行為動詞時，有時態(tài)的變化，后面跟動詞不定式，其否定式和疑問式要用助動詞；dare作情態(tài)動詞時，后面只跟動詞原形，其否定式和疑問式不用助動詞，而是直接在dare后面加上not構(gòu)成否定式，疑問句直接把dare提前。例如： I wonder how she dared to say that. (行為動詞) We wouldnt dare to play with you. (行為動詞) Does she dare to go there alone? (行為動詞) Dare you jump over the ditch? (情態(tài)動詞) She dare not go out at night. (情態(tài)動詞) I dared not tell him the bad news. (情態(tài)動詞) 9. had betterhad better的意思是“最好”，表示建議，相當于Its better for you to.had better后跟省略了to的動詞不定式，即had better do; 其否定式為had better not do, 表示“最好不”。例如： We had better start now. You had better not take the risk.情態(tài)動詞的推測性用法用于推測性含義時，might可能性最小，must可能性最大。1. may和might表示可能性表示“可能性比較大”時，我們用may；如果可能性比較小，我們用might。例如： He might tell his friends. (可能性小) He might be waiting at the gate.(可能性小) He may be at home. (可能性大) Tom may lend you the bike. (可能性大 = It is very likely that.) Tom might lend you the bike.(可能性小 = I think it is unlikely.) might也可以表示“過去的可能性”。例如：If you invited him，he might come.若要表示“不可能”，我們用cant或couldnt。例如：He cant be the manager. He is only a junior clerk.在問句中，may只能用來表示“允許”，不能表示可能性；否則，我們用can, do you think, is it likely that, is it possible that等結(jié)構(gòu)來表示可能。例如： May I come in? (表示許可) Yes, come in please. Where can he be? (表示可能性) He may be in the office.may可與have done連用，構(gòu)成may have done,表示“某一事件在過去發(fā)生的可能性”。例如： Why hasnt she come? She may have missed the train. -He isnt back yet. He may have had an accident.另外，might have done還有虛擬的含義，表示“與事實相反”。例如：You were stupid to try climbing up there. You might have killed yourself.2.can和could表示可能性can和could可以表示“事物實際發(fā)生的可能性”。如果邏輯判斷是現(xiàn)在或說話時刻作出的，用cancould用來判斷可能性，不確定性和委婉的語氣要更強一些。例如：CanCould the news be true? If you dont have a guide, you could lose your way.另外，can的這種用法多出現(xiàn)在否定句中，表示“不可能”。例如：It cantcouldnt be true. The moon cant always be at the full.She cant be serious.can not have done表示“過去的時間發(fā)生的可能性很小”。例如：The door cant have been open for I locked it myself.3. must表示極大的可能性 must的此種用法，指的是邏輯上較大的可能性，表示“一定肯定”,比will和should語氣更強。例如：You must be mad to do that. (干那事你一定是瘋了。) must表示“推測”，通常只用于肯定形式，其否定形式為cant。例如:You must have difficulty getting the tickets. You cant have any difficulty getting the tickets.對過去動作的推測通常用must have done來表示，否定形式是cant have done。He must have taken sleeping pills last night.You cant have left your handbag in the theatre.I dont think he can have heard you. Call again.1) Can I have some sweets? I am hungry. You cant be hungry. Youve just had dinner.2) A man answered the telephone. I suppose it was her husband. It cant have been her husband. He has been dead for ages.must表示猜測的可能性比may的可能性大許多。比較： 1) 鑰匙圈上有三把鑰匙，其中一把是開房門的。當我們拿起其中一把時，我們說： This maymight be the key. (當試了兩把鑰匙門都沒有開后，我們拿起第三把鑰匙。) 這時我們說: This must be the key. (因為這是最后一把鑰匙了。) 2) 看下面的對話 I wonder why Tom hasnt answered my letter. He might be ill. (他可能病了，但也有其他的可能，如他太忙了，等等。) 4. should和ought to表示極大可能性should 和 ought to 的這種用法指通過邏輯推斷得出的極大可能，可以理解為“應(yīng)該是” (= It is extremely likely that.) .例如： That should not be a difficult problem for Kate. (不應(yīng)該是個難題。) It should be ten oclock now. 5. will和would表示預(yù)言在這種用法中，willwould表示“情況肯定會是這樣”。但would的可能性比will小。例如：1) Where is Tom? He will be in the library. 2) There is someone coming. It will be Mary.比較 will 和 should 在推測性用法中語氣的差異： Tom should know the address. (我想Tom應(yīng)該知道 = I expect Tom knows it.) Tom will know the address. (我肯定Tom會知道的 = I am sure Tom knows it.) 從以上的例子中不難看出，will用來表示“猜測”時，語氣比should更加肯定。另外，should表示“推測”不能用于貶義的(或令人感到不悅的) 語境中。例如： Lets not go shopping now. The shops will be very crowded. (這里不能用should) Lets go shopping now. The shops will/should be fairly empty. (這里也可以用ought to) 備注：表示可能性大小的順序為： must will would ought to should can could may might1.would rather, would sooner, would (just) as soon, had rather, had better, had sooner, can not but, may (just) as well等可用作情態(tài)動詞。例如：2）The soldier would sooner die than surrender. The brave soldier would as soon die as yield to such an enemy. Id rather walk than take a bus.If you dont like to swim, you may just as well stay at home.3)would (had) rather, would (had) sooner, would (just) as soon后可跟that 引導(dǎo)的從句，that 常省去，從句要用虛擬語氣。對現(xiàn)在和將來的假設(shè)用過去時，對過去的假設(shè)用過去完成時。例如：I would rather you came on Sunday. I would sooner you hadnt asked me to speak yesterday.4.表推測的情態(tài)動詞句子的反意疑問句He must/may be in the room, isnt he? He cant be in the room, is he？He must have finished the work, hasnt he? He may have done the work last night, didnt he?情態(tài)動詞 + have +done 反義問句的結(jié)構(gòu)由有無時間狀語來決定。Lucy must have worked last night, didnt she?Lucy must have worked , hasnt she? 4.情態(tài)動詞+ have been + v-ing形式 （表示推測或評論過去某動作是否正在進行或一直在進行）They should have been meeting to discuss the problem.三、情態(tài)動詞其它用法1. cannot but do sth. 表示不得不，只好 I cannot but choose to go.2. may well +動詞原形 完全能， 很可能 He may well be proud of his son.3. may as well 最好 We may as well stay where we are.4 cannot ( 或never 等否定詞)與enough 表示再也不為過 You cannot be careful enough.情態(tài)動詞練習(xí)題1. Jack described his father, who _a brave boy many years ago, as a strongwilled manA. would be B. would have been C. must be D. must have been 2.You_ buy a gift, but you can if you want to.A. must B. mustnt C. have to D. dont have to3. I have told you the truth. _ I keep repeating it?A Must B Can C May D Will4. I_ have watched that movie itll give me horrible dreams. A. shouldnt B. neednt C. couldnt D. mustnt5. Mark _ have hurried. After driving at top speed, he arrived half an hour early.A. neednt B. wouldnt C. mustnt D. couldnt 6. _ I take the book out? Im afraid not.A. Will B. May C. Must D. Need7.Just be patient .You _ expect the world to change so soon .A. cant B. neednt C. may not D. whether 8.I havent got the reference book yet, but Ill have a test on the subject next month. Dont worry. You_ have it by Friday.A. could B. shall C. must D. may 9.May I take this book out of the reading room? No, you_ . You read it in here. A. mightnt B. wont C. neednt D. mustnt10.Doctors say that exercise is important for health, but it _ be regular exercise.Acan Bwill Cmust Dmay11.-Good morning. Ive got an appointment with Miss Smith in the Personnel Department. -Ah, good morning. You _ be Mrs. Peters. A. might B. must C. would D. Can12.“You _ have a wrong number,” she said. “Theres no one of that name here.”A. need B. can C. must D. would 13.-Sorry, Professor Smith. I didnt finish the assignment yesterday.-Oh, you _ have done it as yesterday was the deadline.A. must B. mustnt C. should D. shouldnt14. Bob would have helped us yesterday, but he-_A. was busy B. is busy C. had been busy. D. will be busy 15. John went to the hospital alone. If he_ me about it, I would have gone with him.A. should tell B. tells C. told D. had told 16. George is going to talk about the geography of his country, but Id rather he_ more on its culture.A. focus B. focused C. would focus D. had focused17.If we _ the other road, we might have arrived here in time for the meeting. A. take B. had taken C. took D. have taken18.-The weather has been very hot and dry. -Yes. If it had rained ev