1、情态动词（modal verbs)： 表示说话人的语气或情态，如请求、命令、愿望、能力以及可能性等。英语的情态动词有： can/could may/might must shall/should will/would need have to 能够可能必须应该意愿敢需要不得不+ 动词原形 肯定 否定 缩写否定 can can not cant couldcould not couldnt maymay not / mightmight not mightnt must must not mustnt shouldshould not shouldnt needneed notneednt一、情
2、态意义表示法一、情态意义表示法1.表示表示“能力能力”和和“可能可能” a)表示表示“能力能力”，可用，可用can, could, be able to can既能表示现在的能力，也表示将来的能力。既能表示现在的能力，也表示将来的能力。Eg.Look! I can do it. I cant do it now, but I can do it later.现在“能力”：can, be able to As I have got enough money, I can/am able to help her.Can: 1.某桩具体事情：eg.I can climb this cliff.2.泛
3、指一般的“能力”： He can drive a car. She cant play the piano.将来“能力”：通常 will/shall be able to Ill be able to speak German in another two months具体某事：can Can you go and see him tomorrow morning? If I can, I will do it.过去“能力”: could, was/were able to 肯定句：Could：一般能力 She could play the piano when she was only si
4、x. was/were able to(及managed to)：具体事件 He was able to translate the article without a dictionary. I talked a long time, and in the end managed to make her believe me.在否定句中，could既可以表示过去一般能力，也可表示过去某具体事情的能力. I couldnt/wasnt able to play the piano when I was at school.b)表示“可能”，可用may, might, can, could ma
5、y/might：1.既可以表示现在的可能，也可表示将来的可能，might在口气上比may更委婉 现在：It may/might be true. 将来：He may/might leave tomorrow.2.在疑问句中，用can，不用may。 Can they have missed the bus? Yes, they may have.may not重音落在助动词上，表示“不可能”，重音落在否定词上，表示“不许可” , 比较：He may not go tomorrow.He may not go tomorrow.所以在书面语中，表示“不可能”常用cantcan/could表示现在的
6、可能，口气上could比较委婉vThats not mine. Whose can it be?vIt could be Johns.can常用于否定句和疑问句，而could不受此限。vIf you dont have a guide, you could lose your way.vIt cant/couldnt be true.vCan/could the news be true?在肯定陈述句中，may与can的比较：Can指逻辑上的可能性，may指事实上的可能性 The road can be blocked.(按逻辑可能会堵，)The road may be blocked.(可能
7、现在正堵着，事实上) Mr Reed is in poor health. He can be ill at any time. Mr Reed looks pale. He may be ill.“may/might +have done/have been doing”,“can/could +have done”表示过去的可能。vHe may/might have missed the train.vShe may/might have been expressing her true feelings at that moment.vShe cant/couldnt have miss
8、ed the train.“might/could +have done ”可以表示本来可能发生但没有发生的，或者本来可能完成却没有完成的动作，vYou might have finished the work last week.vI could have passed the examination, but I failed.a)请求对方“许可”可用can, could, may, might. may/might较正式，could/might较委婉表示给予“许可”通常用can/may,而不用could/might Could I use your phone? Yes, of cour
9、se you can. Might I trouble you for a light? You may indeed.b)表示“不许”可用may not或者cannotCan I go out for a moment?No, you cant. May I use your car for a few days?No, you may not. may not也可表示根据一般规定的“不许可”，而不是说话人不许可Borrowers may not take out of the library more than two books at a time. may not表示“不许可”的过去式
10、不是might not He may not go.(=I dont permit him to go.)He might not go.(=Possibly he will not go.)过去的不许可：He was not allowed to go.a)表示“义务”，可用should, ought to, must. 表示要求，命令时，语气由ought to、 should、must渐强Should/ought to表示“应该”，带有敦促，劝说之意，可交替使用，前者语气更强。You should/ought to drink less.Should/ought to +have done
11、:本应该You should/ought to have asked my permission first.Must表示敦促或命令，必须。I really must stop smoking.表示将来的“必须”，常用have to的一定形式（will/shall have to) 比较：We must do it again.(表示现在)Well have to do it again.(表示将来)表示过去的“必须”，常用had toI had to leave at six yesterday.must有两种否定形式:第一个是must not,表示“不许”、“禁止”,相应的半助动词是be
12、to的否定形式be not toYou mustnt talk like that.You are not to talk like that.(不许你如此讲话。)第二个否定形式是neednt,表示不必。与neednt相当的动词形式是dont need to/dont have to/havent got toA: Must you leave soon?B: No, I neednt/dont need to/dont have to/havent got to.必须：must与have tomust侧重于说话人的主观意志 have to侧重客观需要 He must say it in En
13、glish. (I want him to do so.)He have to say it in English. (He doesnt know Chinese.) 在特定语境中，用will也可表示“义务”，常用于第二人称主语，这实际上是强化的祈使句。You will wait outside the gate.Brian! You will close the door.b)表示“必然”，可用should，ought to和must(一般用于陈述句)，其中must口气最为肯定。都指说话人根据一定情况做出推测或判断.She should be here in a minuteThese y
14、oung trees ought to provide shade in ten years .All men must die.ought to(表示“推测”）的否定形式是oughtnt toYou oughtnt to have any difficulty getting the tickets.如果是推测过去的事态，则用must +have doneYou must have left your handbag in the theatre.表示推测的must的否定形式是cant不是must notIf Fred didnt leave home before five, he can
15、t be there yet.a)表示“预见”，即表示“单纯将来”，可用will/shall+不定式，shall用于第一人称，will用于第二、三人称。现在一般will可用于一切人称表“将来”I will be a different person when I live in England.You will be hearing from me.She will probably last longer than you will.It will rain tomorrow.非正式语体中，will常用语第一人称主语表将来，常用will、shall的缩写ll，模糊了其界限。Ill come
16、in after church and give you a hand.b)表示“推测”，除用should, ought to,和must外，还可用will/would（语气仅次于must）。They should/ought to be home by now.(他们现在该到家了)They would be home by now.(他们现在大概到家了)They will be home by now.（我估计他们现在一定到家了）They must be home by now.（他们现在一定到家了）will/would表示“推测”可有三种情况 1）对特定事态的推测 A: Whos that
17、 man over there? B: That will be George, no doubt. C: That would be George, I except.2）对某些习惯性事态的推测，will指现在习 惯，would指过去习惯vHe will work all day without a rest.vBefore his retirement he would catch the early bus every morning.3）对某些不受时限的客观过程的推测，只用will,表示现在时间，可与一般现在时的类似用法交替使用。 Pigs will eat anything.=Pig
18、s eat anything.5表示“意愿”、“意图”和“决心”，a)表示意愿都可用will, would, shall。 will用于一切人称的主语,可缩写，will相当于be willing to ,I will lend you the money if you need it.My sister will help you with the luggage.You can help me if you will.Will用于第二，三人称的疑问句，是询问别人是否愿意做某事，请求Will you please open the door for me?此时，will=would you,
19、would you please, would you be good enough to ,would you like to, would you be so kind as to表示接受请求时，用will不用wouldWould you lend me your pen a minute?Certainly, I will.表示不愿意，用will not/wontI will not do anything solely for money.表示过去的意愿或者不愿意用would, wouldnt,间接引语I asked him if he would help me with my wr
20、iting.shall一般用于第二、三人称主语，表示说话人的意愿,而不是句子主语的意愿，在疑问句中表示征询听话人的意愿You shall stay with us as long as you like=Im willing to let you stay with us as long asHe shall be praised if he works hard for the people=Ill see that he is praisedShall you take a holiday this summer?b)表示意图，同上a)用法一致。c)表示决心，同上shall表示“决心”时，
21、否定形式为shall not /shant，表示说话人禁止、威胁No one shall stop me.a)should可在某些语境中表示惋惜、忧虑、欢欣、惊讶等感情色彩。例如在某些that-分句，惯用的疑问句和感叹句中。 How should I know?That he should dare to attack me!还可用在某些语境中并不表示具体的情态意义。例如在be-型虚拟式中或状语分句中。I insisted that he go/should go with me.They got warmly dressed for fear that they should catch c
22、old.此外，should还可以和say，think搭配表示婉转口气。I should say he is just the right man for the job.b) would可用于委婉的简述，客气的请求,委婉的建议I dont think he would be so careless.(委婉的陈述)Would you like to stay here for the night?(客气的请求)Wouldnt it be better for us to start off a little earlier tomorrow morning？(委婉的建议)c)作为情态动词表示“胆
23、敢”，dare通常只用于否定陈述句和疑问句,I dare not go there.多用于现在时形式，但它既可以指现在时间，The presidet was so hot-tempered that no one dare tell him the bad news.也可指过去时间。否定形式为darent。 Tom wanted to come, but he darent. dare用作主动词，通常用于否定句和疑问句。 He does not dare (to) answer. dare的过去式dared通常只用于文学语言等正式语体，也还是用于否定意义。Nobody dared lift t
24、heir eyes from the ground.d) need表示“必须，需要”，做情态助动词，只用于否定句和疑问句，He neednt worry about it.作情态助动词，答语肯定，must；否定，neednt Need we work late today? No, but we must tomorrow. Need I tell Elizabeth at once? No, you neednt tell he just yet. 询问对方是否需要，必须做某事，可用need，也可用must, 否定用neednt或dont have to A: Must I see a do
25、ctor at once? B: No, you neednt/dont have to see a doctor for the time being.Neednt +have done，表示过去本来不必做的事却做了You neednt have bought that house.Didnt need to 与neednt have +-ed比较：I didnt need to go to the station.(因无必要不曾前往)I neednt have gone to the station.(本无必要却在过去某时去了)e) used to(只有过去时形式，没有现在时形式）表示过去
26、习惯动作或状态，这种状况已不复存在。 He used to live in Shanghai, usedt he?在否定陈述句或否定疑问句中，用didnt use to或usedt to均可。He didnt use to smoke cigarettes=He usednt to smoke cigarette. 在肯定疑问句中有两种形式： Used you to ?/Did you use to?Used you to go to the same school as Edward?=Did you use towould表示表示“习惯习惯”时，可与时，可与used to交替使用，区别在于
27、交替使用，区别在于would只与动态动词连用，只与动态动词连用，通常用于正式语体。通常用于正式语体。17.2 情态助动词的推测性用法和非推测性用法情态助动词情态助动词非推测性用法非推测性用法推测性用法推测性用法can/could“能力能力”、“许许可可”“可能可能”may/might“许可许可”“可能可能”will/would“意志意志”“推测推测”Should/ought to“义务义务”“必然必然”must“义务义务”“必然必然” uncertain might may could can should ought would will certain must 1)直接引语中，说话人的主观看法总是以现在时间 为基点的。2)说话人所推测的事件所发生的时间，要根据不定式所采取的形式而定。 不定式若为非完成体形式则表示现在时间或将来时间；不定式若为完成体形式则表示过去时间。 He must be there.=Im sure he is there. He must have gone.=Im sure he has gone. went. .Thanks for your viewing!
