情态动词用法讲义

1、情态动词的用法在英语中，情态动词属于助动词。除了作简略回答外，它们一般不能单独使用，它们必须与动词原形一起使用构成句子的谓语。不同的情态动词会有不同的意义和用法。有时，同一个情态动词在不同的语境中也会产生不同的含义。情态动词的推测性用法和非推测性用法11情态动词一般有两种用法：推测性用法和非推测性用法。推测性用法是指做出推测，预测事物发生的可能性；非推测性用法则指情态动词本身的基本含义,如can表示能力，may 表示许可，must 和should 表示必须和义务，need表示需要等。例如:I can swim.（非推测性用法）This can be true.（推测性用法）You may go

2、 now.（ 非推测性用法）He may be ill now.（推测性用法）You must finish it before lunch time.(非推测性用法）He must be at home for he never goes out at dinner time.(推测性用法）我们把英语中的9大情态动词按其推测性和非推测性用法列表如下情态动词非推测性用法推测性用法:an / could能力 /许可(ability / permission)可能(P ossibility)may /might许可(p ermission)可能(P ossibility)will /would意愿

3、(volition)预言性(predictability)should / ought to责任和义务（obligation）应该是(logical necessity)must责任和义务（obligation）一定，肯定(logical necessity)情态动词非推测性用法的说明1. may和might 表示允许may可以与不同的人称搭配，表示“许可、允许”。例如:我允许你第一个离开。）May I know your name?我允许你借。）You may be the first to leave if you are in a hurry.(You may kee p the boo

4、k for two months.(In certain circumstances a p olice officer may ask a driver to take a breath test.May I come in?may用在疑问句中，经常表示允许、许可”的意思。例如：May I know your name?的过去式)might可以用来表示过去时态，也可以表示委婉语气。例如：She said that he might take her dictionary. (mayMight I have a word with you?(委婉用法)I wonder if I might h

5、ave more salad.(委婉用法)但在回答中，我们一般用 may 加强肯定的语气，而不用 might .例如：Yes, of course you may.may not可用来表示“禁止”或“不许”，因语气较强，所以不用might not. 例如:Students may not stay out of the dormitory after midnight without written p ermission.must not 也可以表示“禁止”，而且语气比 may not更强，强调上级对下级的不允许。另外，may/might as well也是一个常用的词组，后接动词原形，意思

6、是“不妨，最好” 相当于 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。但若要表示在过去某个具体场合下能够做某事的能力，我们用was/were able to.例如: Thank you for your help. I m glad I was able to help you.(在这种情况下能够帮你，而且已经帮了。)所以was/were able to不仅表示过去的某个具体场合下的能力，还强调动作已经成功完成，相当于manage

7、to do 或 succeed in doing. 例如:We were able to save him.(把他救活了。He was able to expl ain what had happ ened.(他能解释，而且也解释了He could expl ain what had happ ened.(他能做出解释，但可能没有说。但这种区别只局限在陈述句，在否定句中,be able to 和could 可以互换。有时，could 表示的并不是 can 的过去式，而是一种委婉的语气。例如:Could you run the business yourself? Could you pl ea

8、se give me your reply as soon as p ossible?。例如:could have done有虚拟的含义，即“本来能够做，但事实上却没有做”You could have told me earlier. I could have p assed the exam if I had worked harder.2)表示许可can 也可以用来表示“允许” ，例如:Can I smoke here? The p oliceman says we cant park our car here.could可以使句子更显礼貌，但在肯定回答中，我们一般用can代替could,

9、加强肯定的语气。即： Yes, of course you can.3）其他用法can not与help, bear, stand等动词连用，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can t help but后面接动词原形，表示“只能”I can not help but ask you:do you have loved me?I can t help but wait.3. must表示必须must的这种用法，体现了说话者的权威性，所以must

10、通常用于上级对下级、长辈对小辈例女n: You must be back by ten oclock.Teacher: You must use a dictionary. I m tired of your spelling mistakes.注意 must 和 have to 的区别： must 表示出于说话者本人的主观愿望，必须去做某事； 而 have to表示受外部条件的影响，不得不做某事例如：I must leave now.（ 我自己想离开，主观愿望。）I have to leave now.（也许我还想坐一会儿，但我有要事，不得不走了。He must say it in Engl

11、ish.（除了英语，他可能还懂其他语言，但我的主观愿望是他必须说英语。He has to say it in English.（客观条件是他只懂英语，所以不得不用英语说。）另夕卜，由于 must 没有将来时态，所以我们通常用will /shall have to来表示；由于 must 没有过去时态，所以我们通常用had to 来表示。例如： We will have to do it again.l had to leave at 6:30 yesterday.但有时，我们也可以在表示过去的上下文中使用must .例如：I told him that he must mind his own

12、business.must 有两种否定形式：mustnt 和 neednt / dont have to.mustnt 表示 不可以“，neednt / dont have to表示“不必”， 例如： You mustnt talk like that.( 不可以 =You are not allowed to talk like that.)No, I neednt. Must you leave so soon?4. should 和 ought toshould 和 ought to通常可以交互使用，意义没有多大的区另U，表示“应该”。should 和 ought to 的这种用法通常表

13、示“建议、敦促或怂恿”比较must, have to 和should /ought to所表示的不同语气：钢琴老师对某学生说：You must p ractice at least an hour a day. (must显示了老师的权威。)这个学生然后对他的朋友说：I have to p ractice an hour a day! (have to表示我本身不想练，但迫于老师的压力，不得不练。)他的朋友会说：You ought to / should p ractice for more than an hour.(表示不是来自外界的权威或压力，而是来自平辈同学或朋友的建议：如要做个好学生

14、，弹好钢琴。另夕卜，should have done /ought to have done 表示 “本该发生的事没有发生;例如： You should have told me earlier. You ought to have been more careful.5. will 和 wouldwill和would作情态动词使用，主要有以下的用法:1)表示意愿will和would 表示的意愿可强可弱，意愿弱时表示“愿意做某事”(willingness);意愿强时表示“坚持要做某事” (insistence).例如:Will you go with us?( 愿意) Will you p a

15、ss me the salt?( 愿意)Let us have a talk, will you?( 愿意)I will marry her although my p arents are strongly against our marnage.(表示坚持)would 可以表示“过去的愿意” ， 一般用于间接引语中 ，例女口 :He said he would come.在其他情况下，would 不表示过去，而表示 委婉的语气 “，例如： Would you please make a copy forme?但在回答中，为了加强肯定的语气，我们用 will .例如 Would you le

16、t me hear from you soon? Yes, I will.2) 表示能力、趋势或必然性will和would 的这种用法一般以东西作为主语，表示“其内在的性能或特征性倾向”例如： Oil will float on water.Gold wont dissolve in acid.否定形式won t还可以表示“某事没有达到我们期望的效果”例如:The car wont start. The door wont open.注意这里用主动语态。3)表示习惯性的动作。例女口 :Every morning he will sit in the office doing nothing.H

17、e will often say something and then forget it.在这种用法中，would是will的过去式。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“说话者的决心或承诺”例如： I shall never give up. The invaders shall be wiped out.Yo

18、u shall get your salary tomorrow. (I p romise.)He shall get his share. (I p romise.)You shall stay with us as long as you like. (I p romise.)2）表示“命令”，语气很强。例如： You shall go at once.You shall do as I say.You shall never tell lies.此种语气因太专横，所以一般不用，但在法律文件和合同条款中，我们通常用shall表示权利和义务。3）疑问句中用来征求意见例如： Shall I p

19、ick 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可以作行为动词，也可以作情态动词。need作行为动词时，有时态的变化，后面跟动词不定式或名词，其否定式和疑问式要用助动词；need 作情态动词时，后面只跟动词原形，其否定式和疑问式不用助动词，而是直接在 need 后面加上 not 构成否定

20、式，疑问句直接把need 提前。例如： You neednt come.（ 情态动词）I wonder if we need take slee ping bags.(情态动词）I need your help.(行为动词)I need to have a look.(行为动词) Need we work today?( 情态动词) Yes, we must. (No, we neednt.)need作情态动词，表示“需要”，常用在否定句、疑问句或if引导的从句中，在回答need引导的问句中,肯定回答用must加强语气，表示“必须”；否定回答用needn t,表示“不必”，相当于not hav

21、e to.Needn t have done 表示“没有做某事的必要，该事本不必做，但却做了”don t need to 只是表示“不必做某事，而且该事也确实没有做”例如：I didnt need to go to the station.(没有去车站 )I neednt have gone to the station.(去了车站）8. daredare可以作行为动词，也可以作情态动词。dare作行为动词时，有时态的变化，后面跟动词不定式，其否定式和疑问式要用助动词；dare作情态动词时，后面只跟动词原形，其否定式和疑问式不用助动词，而是直接在dare后面加上not构成否定式，疑问句直接把d

22、are提前。例如： I wonder how she dared to say that.( 行为动词)We wouldnt dare to play with you.(行为动词) Does she dare to go there alone?(行为动词）Dare you jump over the ditch?(情态动词)She dare not go out at night.( 情态动词)I dared not tell him the bad news.(情态动词）9. had betterhad better 的意思是“最好”，表示建议，相当于 It s better for y

23、ou to.had better后跟省略了 to的动词不定式，即 had better do;其否定式为 had better not do,表示“最好不”。例如： We had better start now. You had better not take the risk.情态动词的推测性用法用于推测性含义时，might可能性最小，must可能性最大。1. may和might表示可能性表示“可能性比较大”时，我们用may ;如果可能性比较小，我们用might 。例如： He might tell his friends.(可能性小）He might be waiting at the

24、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“过去的可能性”。例如：If you invited him ， he might come.若要表示“不可能”，我们用 can t或 couldn t。例如： He can t be the manager. He is only a junior clerk.在问句中，m

25、ay 只能用来表示允许”，不能表示可能性；否则，我们用 can, do you think, is it likelythat, is it p ossible that等结构来表示可能。例如： May I come in?( 表示许可) Yes, come in pl ease. Where can he be?( 表示可能性)一 He may be in the office.may 可与 have done 连用，构成 may have done, 表示 “某一事件在过去发生的可能性”例n： Why hasn t she come? She may have missed the tra

26、in.-He isn t back yet. He may have had an accident.另外，might have done还有虚拟的含义，表示“与事实相反” 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“事物实际发生的可能性”。如果逻辑判断是现在或说话时刻作出的，用cancould用来判断可能性，不确定性和委婉的语气要更强一些。t have a guide, you could lose your way.例如：

27、Can /Could the news be true? If you don另外，can的这种用法多出现在否定句中，表示“不可能” 例如：It can t/couldn t be true. The moon can t always be at the full.She can t be serious.can not have done 表示“过去的时间发生的可能性很小” 例如：The door can t have been open for I locked it myself.3. must表示极大的可能性must的此种用法，指的是逻辑上较大的可能性，表示“一定肯定”，比will和

28、should 语气更强。例如：You must be mad to do that.（干那事你一定是疯了。）must表示“推测”，通常只用于肯定形式，其否定形式为 can t。例女口:You must have difficulty getting the tickets.You can t have any difficulty getting the tickets.对过去动作的推测通常用 must have done来表示，否定形式是 can t have done 。He must have taken slee ping p ills last night.You can t hav

29、e left your handbag in the theatre.I don t think he can have heard you. Call again.1) Can I have some sweets? I am hungry.You can t be hungry. You ve just had dinner.2) A man answered the tele phone. I supp ose it was her husband.It can t have been her husband. He has been dead for ages.must表示猜测的可能性

30、比 may的可能性大许多。比较:1）钥匙圈上有三把钥匙， 其中一把是开房门的。当我们拿起其中一把时，我们说：This may /might bethe key.（当试了两把钥匙门都没有开后，我们拿起第三把钥匙。)这时我们说：This must be the key.( 因为这是最后一把钥匙了。）2)看下面的对话一I wonder why Tom hasn t answered my letter.(=It is 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表示极大可能性should 和ought to的这种用法指通过

31、逻辑推断得出的极大可能，可以理解为“应该是” extremely likely that.)不应该是个难题。)例如： That should not be a difficult p roblem for Kate.(It should be ten oclock now.125. will和would 表示预言在这种用法中，will /would 表示“情况肯定会是这样”。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.比较will和

32、should 在推测性用法中语气的差异:Tom should know the address.( 我想 Tom 应该知道 =I expect Tom knows it.)Tom will know the address.( 我肯定 Tom 会知道的 =I am sure Tom knows it.)从以上的例子中不难看出，will 用来表示“猜测”时，语气比 should 更加肯定。另外， should 表示推测”不能用于贬义的(或令人感到不悦的)语境中。例如： Let s not go shopping now. The shops will be very crowded.(这里不能用

33、should)Let s go shopping now. The shops will/should be fairly empty.(这里也可以用 ought to)备注：表示可能性大小的顺序为: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) aswell等可用作情态动词。例如：2) The soldier woul

34、d sooner die than surrender. The brave soldier would as soon die as yield to such an enemy. I rather walk than take a bus.If you don t 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 引导的从句，that 常省去，从句要用 虚拟语气。对现在和将来的假设用过去时，对过去的假设

35、用过去完成时。例如：I would rather you came on Sunday. I wou ld sooner you hadn t asked me to speak yesterday.4.表推测的情态动词句子的反意疑问句He must/may be in the room, isne he? t be in the room, is heHe must have finished the work, hasnHembhehave done the work last night, didn情态动词+ have +done反义问句的结构由有无时间状语来决定。t he?Lucy m

36、ust have worked last night, didnt she?t she?Lucy must have worked , hasn4.情态动词+ have been + v-ing形式(表示推测或评论过去某动作是否正在进行或一直在进行)They should have been meeting to discuss the p roblem.三、情态动词其它用法1. cannot but do sth. 表示不得不，只好 I cannot but choose to go.3. may as well 最好2. may well +动词原形 完全能， 很可能 He may wel

37、l be proud of his son.We may as well stay where we are.4 cannot （ 或 never 等否定词）与 enough 表示再也不为过You cannot be careful enough.情态动词练习题1. Jack described his father, whoa brave boy many years ago, as a strong-willed man14A. would be B. would have beenC. must beD. must have been2.YouA. mustB. mustntC. hav

38、e toD. dont have to3. I have told you the truth.I keep repeating it?A MustB CanC MayD Willbuy a gift, but you can if you want to.4. IA. shouldn t B. needn tC. couldn t D. mustn thave watched that movie itll give me horrible dreams.5. MarkA. needn tB. wouldn tC. mustn tD. couldn t6.I take the book ou

39、t?have hurried. After driving at top speed, he arrived half an hour early.Im afraid not.A. WillB. MayC. MustD. Need7.Just be patient .Youexpect the world to change so soon .A. can tB. needn t C. may notD. whether8. I haven t got the reference book yet, but I ll have a test on the subject next month.

40、Dont worry. Youhave it by Friday.A. couldB. shallC. mustD. may9. May I take this book out of the reading room?No, you. You read it in here.A. mightn tB. won tC. needn tD. mustn t10. Doctors say that exercise is important for health, but itbe regular exercise.A canBwillC mustDmay11. -Good morning. Iv

41、e got an appointment with Miss Smith in the Personnel Department.-Ah, good morning. Yoube Mrs. Peters.A. mightB. mustC. wouldD. Can12.“Youhave a wrong number,” she said.Theres no one of that name here.A. needB. can C. mustD. would13. -Sorry, Professor Smith. I didnt finish the assignment yesterday.-

42、Oh, youhave done it as yesterday was the deadline.A. mustB. mustntC. shouldD. shouldnt14. Bob would have helped us yesterday, but he-A. was busyB. is busyC. had been busy. D. will be busy15. John went to the hospital alone. If heme about it, I would have gone with him.A. should tellB. tellsC. toldD.

43、 had told16. George is going to talk about the geography of his country, but Imdorreatohneritshec_ulture.A. focusB. focusedC. would focusD. had focused17.If wethe other road, we might have arrived here in time for the meeting.D. have takenA. take B. had taken C. took18. -The weather has been very hot and dry.-Yes. If