1、情态动词（Modal Verbs),can, could, may, might, will, would, shall, should, must和ought称为情态动词。它们和主要谓语动词一起构成谓语。绝大多数情态动词的意思可以划分为两类。一类是表示可能性：情态动词可以用来表示某种情况是肯定的、或很可能的、或可能的、或不可能的。,另一类意思涉及必须做某事或允许做某事之类的意思：情态动词可以用来表示某人必须做某事、某人能做某事，如果某事发生（或不发生）就会好一些，或者某事是许可或禁止的。,一、表示有把握的程度情态动词可以表达对于某一事实或事件有把握的各种不同程度。,a完全有把握(肯定的或否定
2、的）,shall用于第一人称：I/We shall be away tomorrow.I shant be late on Wednesday.2. will 用于各种人称：Thats the phone. Thatll be Tony.Things will be right.It wont rain this evening.Youll be right.,3. must只用于肯定句中：He decided Franklin must be suffering from a bad cold.4. cant和couldnt表示现在或将来不可能，couldnt用于间接引语中，表示过去不可能：
3、That cant be Mr. Smithhes in New York.I knew it couldnt be Mr. Smith.He couldnt be at home.5. would, wouldnt 用于间接引语中，表示过去可能或不可能：I told you wouldnt be ready in time.,1. should, shouldnt, ought to, oughtnt to, may well (很有可能）, may, may not （可能、可能不） : She should/ought to be here soon.It shouldnt/oughtn
4、t to be difficult for you to work out the problem.3. We may be buying a new flat.4. The list may not be complete.5. “I think its going to rain.” “You may well be rightthe sky is really black.,b很有可能/可能,C可能性小,might, mightnt, could,它们不是may, can的过去式，它们都可以用来谈论现在和将来, could比may 和might更不可能：I might see you a
5、gainwho knows?Things might not be as bad as they seem.We could all be millionaires one day.,d在理论上可能或现实可能性,can可以用于肯定句中表示理论上的可能性，或与be动词连用，表示有时：1. Poor posture (姿势）can cause neck ache, headaches and breathing problems.2. New England can be very warm in September.3. Can gases freeze?,2.表示某事将会实际发生，或真实情况的
6、现实可能性通常用may, might或could:1)-I think Labour are going to win. -You may be right.2)-Where is Emma? -I dont know. She may be out shopping.3) Peter might call. If he does, ask him to ring later.4) She didnt say hello. She may not have recognized you.5) -Wheres Sarah? -She may/ might/ could be at Joes pl
7、ace.,e在条件句中表示有把握或可能,would, wouldnt, could, couldnt, might, mightnt可以用在含有条件句的主句中表示可能：If we had enough time, things would be easy.I wouldnt do this if I didnt have to.If John came we could all go home.I couldnt do anything without your help.It mightnt be a bad thing if we took a short holiday.,询问可能性,m
8、ight表示可能性,可以和could/can一样用在问句中，询问可能性。也可用于肯定、否定句中。 Might it be possible to make computers the size of a pinhead one day? Might/ Could/ Can he still be working? Might/ Could/ Can he have been waiting long?4. Might/ Could he have left by tomorrow?,“could, might, ought to, should, would和neednt +have +过分的
9、用法,1.could, might, ought to, should, would和neednt + have +过分,常用来表示非真实的情况:Did you see him fall? He could have killed himself.2. You should have called-I was getting worried.3. I would have gone abroad if I had had more money.4. She neednt have sent her mum flowers.,情态动词modal verbs,的 特点1）有特定的词义2）没有人称和
10、数的变化3）其后加动词原形(do), have done ,be doing.,情态动词,情态动词,1。区别must / have toMust表示人在主观上认为的必要、必须、一定要Have to表示受环境或习惯支配的客观必要 “不得不”，能用于更多时态。 1)Soldiers _obey officers. 2)Its raining outside.We_stay at home.3As he had broken his leg， he _lie in bed.,易混易错用的情态动词,must,have to,had to,2。表示能力: can, could, be able to *
11、be able to 能用于各种时态。 can / could 只能表示现在或过去的能力。 *was / were able to : “设法做成某事” 相当于 managed to do sth. succeeded in doing sth.。Eg.Though they were trapped in the big fire, they _escape.,were able to,4。注意对need问句的回答: -Need I finish the work today? -Yes, _. No, _. No, _.,you must,you neednt,you dont have
12、to,-Shall I tell John about it? -No, you _. -Must we do it now? -No, you _.,neednt (dont have to),neednt(dont have to),6.表示推测情态动词的重要用法.,肯定的推测可能的推测否定的推测疑问的推测,must,对将来 对现在 对过去,情态动词,may, might,cant, couldnt,can, could,+ V. + V. + have done常见must be + be doing,+ V. + V. + have done + be doing 可以用not表示“可
13、能不”,+V. + V. + have done + be doing,+ V. + V. + have done + be doing,2. can (用于疑问句中）， cant, could, may, might, should, ought to, will, must + have + 过分可以表示对过去发生的事情作出推断：Where can he have gone?We cant have taken it upstairs this morning!I may / might/ could have come to a wrong conclusion.4. That was
14、a bad place to go skiing. You might have broken your leg.,5. -A woman phoned while you were out. -It must have been Kate.John should/ ought to have arrived yesterday.7. I wonder why we havent heard from him- do you think he wont have got our letter yet?8. We cant go and see them now- theyll have gon
15、e to bed.,3.can (用于疑问句中）， cant/ could/ may/ might/ should/ ought to/ will/ must + have + 过分也可以表示某事可能已经发生，该用法类似现在完成时和将来完成时：1. Ill try phoning him, but he might have gone out by now.2. By the end of this year I might have saved some money.3. John should /ought to have left by tomorrow.4. Thatll have b
16、een Roland. He said hed be back at 7 oclock.,二、表示必须和允许做某事,情态动词可表示必须和允许做某事的各种含义。情态动词的这类用法很重要，可以有礼貌地表达请求、建议、邀请和批示。a must, will, need (用于疑问句中）强调必要性；shall(用于二、三人称表示说话人的意愿、承诺、命令或法律、规章、制度上要求必须做的事情） ：,Teachers of English must be in the classroom by 7.10.All sales staff will arrive for work by 9.00.Need I g
17、et a visa for Hong Kong?You shall have the book as soon as I finish it.He shant come here.He shant pass the math exam.A record shall be kept of the number of students attending each class.,8. “Can someone help me?” “I will.”9. Ill definitely pay you back next week.10. Ill kill her for this, Sue said
18、.11. “Give me a kiss.” “No, I wont.”12. The car wont start.would指过去愿意；wouldnt指过去拒绝：My husband would do the dishes, but he wouldnt cook.I asked him politely, but he wouldnt tell me.The car wouldnt start this morning.,must, have to 和have got to,这三种形式一般可以互换，用于第一人称时，可以表示 “客观上必须”，在下列情况下，have to/have got
19、to也许比must更合适： We have to/ have got to send these VAT forms back before the end of the month.(即法律要求我们这样做） 另一方面，must可表示说话人认为自己有权做某事，下列句中用must可能比have to/have got to更合适： I/ We really must do something about the weeds in the garden.(别人不会要求我们）,must （不用have to/ have got to) 用于公告或文件中： Cyclists must dismount
20、. Candidates must choose five questions.在表示“非得，偏要”时，一般用must: Must you always interrupt me when Im speaking?must也可以表示恳切的邀请： You really must come and see us some time.must还可以用于强调劝告： You really must take a holiday this year.,b 我们可以用will you告诉人们做什么; would you语气更婉转、更客气。Will you?可以表达人们的愿望；Wont you?表示恳切地劝人
21、接受; could, would表示请求别人为我们做事 ：,Will you send me the bill, please?Come this way, will you?Will you be quiet!Would you open the window, please?Would you mind standing up for a moment?Come this way, would you?Will you have some more dessert?What will you drink?Wont you have some more toast?,You mustnt d
22、rive fast. Theres a speed limit.Magazines may not be taken out of the library.You cant come in here without permission.,c 禁止 mustnt, may not, cant 可以表示禁止，may not非常正式，在非正式文体中cant更常见；mustnt比may not 更为强调：,If you will come this wayI should be grateful if you would let me know your decision as soon as po
23、ssible.Ill pay for the drinks.Anyway, youre here. You might as well stay.Shall I give you a hand?,e 许可:can, may, could/might (用于征求许可)，给予许可时要用may, can:,1. -Can I borrow your laptop?2. -Could I ask you something if you are not too busy? -Yes, of course you can. (不能用You could)3. -Might I come in? -Of c
24、ourse, you may. (不能用might)4. May I use your mobile phone?5. Do you think I might take a break?,f 没有必要:neednt do, neednt have done(表示过去没有必要做而实际做了的事情；didnt need/didnt have to do表示过去没有必要做而实际也未做的事）,You neednt work this Saturday.You neednt have watered the flowers, for its going to rain.I didnt have to c
25、ut the grass myself. My brother did it.,g 表示能力：can, could只有现在时和过去时, be able to do有更多的时态。表示过去的能力和在否定句中表能力时，用could和was/were able to do均可：Jim could/couldnt /was/wasnt able to run very fast when he was a boy.He said he could see me next week. 表示成功地完成某一具体动作时，通常不用could，而用was/were able to/ managed to/succe
26、eded in + doing：In the end they were able/managed to rescue/succeeded in rescuing the cat on the roof.,其他意思： 1. must 可以表示偏要：If you must drink so much, of course youll feel sick.Naturally, after I gave her my advice, she must do the opposite.2. will可以表示常常，would可以表示过去习惯性的行为。used to用来谈论习惯性行为或习惯性状态，而wou
27、ld只可谈论习惯性行为:,Most evenings hell just sit in front of the TV and go to sleep.When we were kids, my mum would take us out on bikes all around the countryside.She will fall in love with the wrong people.If something breaks down, and you kick it, it will often start working again.I used to/ would go swi
28、mming every summer when we were children.He used to have an old Rolls-Royce. (不用would),3 dare,dare 和need 一样，可以作情态动词和行为动词，在意义上区别不大。 dare作为情态动词不如need和used to常用，常用(not) be afraid to或not have the courage to do来表示。作为情态动词dare多用于疑问句和否定句，很少用于肯定句，除非句中含有否定意义：,1. -Dare you do it? -I dont dare do it.2. I hardly
29、 dare tell him what happened.与do/did/does一起构成疑问句和否定句比较常见：“Do you dare tell him?” “I dont dare tell him.”“Did you dare tell him?” “I didnt dare tell him.”do/ dont/ did/ didnt dare to do中带不带to意思一样。,3. dare表示提出挑战, 此时作行为动词:I dare you to jump off that wall .I didnt want to do it, but he dared me (to).4. How dare you 和dont you dare表示气愤：How dare you talk back to me!Dont you dare go anywhere else, you hear?5. dare say/ daresay, 用于第一人称，表示I suppose,或its possible, 或者同意你说的话:I daresay you will phone me if youre going to be late tonight.,
