情态动词讲义

情态动词（情态动词（Modal VerbsModal Verbs）一一.can,may,must.can,may,must 作为情态动词作为情态动词的特点的特点 1.1.不可单独作谓语。不可单独作谓语。2.2.情态动词后需加动词原形情态动词后需加动词原形3.3.情态动词无人称和数的变化情态动词无人称和数的变化二二can,may,must的具体用法的具体用法1.can/could非推测性用法非推测性用法 能力能力 “许可许可 可以可以”I can climb this tree.He can read books.Can I help you?注意：注意：Can I smoke here?Yes,you can.No,you cantI can speak English,but I couldnt 3 years ago.Could 表过去的能力和许表过去的能力和许可。可。Father said I could swim in the river.I could swim when I was only six.Could you wait a few days?Yes,I can.(could you比比can you语气更客语气更客气气,婉转婉转)You can go now(客观允许客观允许).=you may go now（主观）（主观）Can 与与be able toCan只有两种时态只有两种时态 can,could，be able to 有除进行时以外的所有时态。有除进行时以外的所有时态。Can表示一贯的能力表示一贯的能力，be able to表示表示客观能力和通过努力可以达到的能力客观能力和通过努力可以达到的能力I cant swim.But I am sure I will be able to swim through more practicing.The fire spread through the hotel,but everyone was able to get outWhen the boat sank he was able to swim to the bank.B)can/could推测性用法推测性用法 可能可能 He cant be working now.I saw him just now.Can it be true?He cant be Marys father.He is too young.注意注意1)can/could推测性用法推测性用法“可能可能”，can用于否定和疑问句中，不用于肯定用于否定和疑问句中，不用于肯定句中句中,could可用于肯定句中可用于肯定句中.You could be right,I suppose.My wife is in hospitalour baby could arrive at any time.2).can/could 表示对过去的推测是，表示对过去的推测是，用用can/could(not)have doneHe cant have gone to work.It is Sunday.Where can Tom have gone?She could have gone to the cinema.He cant have seen me yesterday.3).can用于肯定句，可表一时的可能用于肯定句，可表一时的可能性，性，”有时可能有时可能”A horse in the centre of London can cost a lot of money.You can walk through the forest for miles without seeing anyone.Old newspapers can be useful.could 加完成式用于肯定句时，一般表加完成式用于肯定句时，一般表过去可能完成而却未完成的动作。虚拟过去可能完成而却未完成的动作。虚拟语气语气 I could have passed my examination easily but I made too many stupid mistakes.-They managed to take me though there were 5 people in the car.-It couldnt have been a comfortable journey.2.may/mightA).非推测性用法非推测性用法 许可许可 可以可以You may leave at once.You may help her.May I come in?Yes,you may.No,you cant No,you may not.No,you mustntNo,youd better not.注意注意:1.May I stay here?在疑问句中在疑问句中主语只用于第一和第三人称中。主语只用于第一和第三人称中。2.You may not come in.你不可以你不可以来来 may not不可以不可以-Will he come tonight?-He may not.可能不可能不3 Might I use your book?Might I take his idea?Yes,you may.Might I 比比may I语气更客气更礼语气更客气更礼貌。貌。Might I的简单回答为的简单回答为 Yes,you may.B).may/might 推测性用法推测性用法“可能可能”用于肯定和否定句用于肯定和否定句.He may be right.She may be staying at home.He may not come today可能不可能不 He may/might come tomorrow.C).may/might have done 表示对过表示对过去发生行为的推测，含有去发生行为的推测，含有想必想必、也也许是许是的意思。的意思。He might/may have stayed at home yesterday.注意注意:1.只用于肯定和否定句中只用于肯定和否定句中,不用于不用于疑问句中。疑问句中。2.might 比比may可能性更小可能性更小He might get a job-He may get a job.3.He may not come.He cant come.may not 可能不可能不 can not不可能不可能You may/might have had trouble in doing that.He might not have settled the question 4.might have done表示说话人对听话表示说话人对听话人的委婉的责备人的委婉的责备,”本可以做，而未做本可以做，而未做”（主语是第二人称）（主语是第二人称）You might have called me.D).might/may as well do sth.还是还是好了好了,还是还是的好；不妨的好；不妨I might as well give the sweet course a miss.There is nothing to do,so I may as well go to bed.You may as well stay where you are.3.mustA)非推测性用法非推测性用法 必须必须You must be here in time.Must we answer it?Yes，you must.No，you neednt.No,you dont have to.No，you dont need to.You mustnt lend it to others.注意注意:1.must 没有过去式没有过去式He said he must/had to see the doctor.2.mustnt 表示表示“禁止，不允许，不许禁止，不允许，不许可可”You mustnt speak like that3.must/have to/have got tomust 主观看法主观看法 have to客观看法客观看法You must be here at 8 oclock.I have to work here to make money.I must go now.I have to goB)must 推测性用法推测性用法“一定一定,肯定肯定”He must have lived here for a long time.You must be tired,arent you?He must have had an accident,hasnt he?It must have rained last night,didnt it?He must have gone abroad,hasnt he?He must have gone abroad yesterday.She must have studied English before.注意注意:must表推测只能用于肯定句，表推测只能用于肯定句，can用于否定、疑问句用于否定、疑问句。He must be off.He cant be here.C.Must:偏偏偏偏 Why must you do that?As I was sitting down to supper,the telephone must ring.Why must you be so stubborn?(adj.顽固的顽固的,固执的固执的)can,may,must的用法表的用法表 汉意 动词非推测性用非推测性用法法 推测性用法推测性用法 cancould能力能力 许可许可 可以可以用于用于肯定肯定否定否定和疑和疑问句问句中中 可能可能 用于否定和用于否定和疑问句中疑问句中 maymight许可许可 可以可以 可能可能或许或许 只用于肯定只用于肯定和否定句中和否定句中 must必须必须 一定一定肯定肯定 只用于肯定只用于肯定句中。句中。4.need,dare 1)作情态动词作情态动词He neednt pay for it.Need you go now?Yes,I must.No,I neednt.You neednt go so early.She darent do so.Dare you do it?Yes,I dare.No,I darent.How dare you say Im unfair.If they dare come,they will never be back.Need,dare作情态动词时，作情态动词时，只可用于否定句和疑问句，只可用于否定句和疑问句，dare还还可用于条件状语从句可用于条件状语从句无第三人称单数形式，无第三人称单数形式，Need,dare后加动词原形后加动词原形need 无过去式，无过去式，dare有过去式有过去式dared否定句为否定句为neednt.darent.疑问句把疑问句把need，dare提前。提前。You neednt have waken me up;I dont have to go to work today.neednt have done表示过去做了表示过去做了某事，但没有做的必要，某事，但没有做的必要，意为意为“本没本没必要必要”。You neednt have waited for me for such a long time.2)need,dare作实意动词时作实意动词时Does he need to know it?She didnt need to go.Who dares to go?I dont dare to ask her.We need to think it over.Do you dare to stay here?She doesnt dare to ask me.He didnt dare(to)move.注意注意:need,dare作实意动词时作实意动词时need,dare可用于所有的肯定句和疑可用于所有的肯定句和疑问句中问句中有第三人称单数形式、过去式。有第三人称单数形式、过去式。need,dare后加带后加带to的不定式。的不定式。否定句和疑问句要使用助动词否定句和疑问句要使用助动词do,does,did等。等。情态动词的简单回答情态动词的简单回答Can you swim?Yes,I can .No,I cant May I come in?Yes,you may.No,you cant No,you may not.No,you mustnt.No,youd better not.Must I go now?Yes,You must.No,you neednt.No,you dont have to.No you dont need toNeed I do it?yes,you must.No,you neednt.Dare you do it?Yes,I dare.No,I darent.Ought he to go?Yes,he ought(to).No,he oughtnt(to).5.shall和和should的用法的用法(1).Shall用于第一人称，表示征求对方的用于第一人称，表示征求对方的意愿。意愿。What shall we do this evening?(2).Shall用于第一、第三人称疑问句中，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表示说话人征求对方的意见或向对方请示。如：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。人给对方命令、警告、允诺或威胁。You shall fail if you dont work harder.（警（警告）告）He shall have the book when I finish reading.（允诺）（允诺）He shall be punished.（威胁）（威胁）(4).Should表示劝告、建议、命令，其同义表示劝告、建议、命令，其同义词是词是ought to；在疑问句中，通常用；在疑问句中，通常用should代替代替ought to。You should go to class right away.Should I open the window?注意：注意：Should的含义较多，用法较活，现的含义较多，用法较活，现介绍三种其特殊用法。请看下面的句子：介绍三种其特殊用法。请看下面的句子：I should think it would be better to try it again.我倒是认为最好再试一试。我倒是认为最好再试一试。You are mistaken,I should say.I should advise you not to do that.我倒是劝我倒是劝你别这样做。你别这样做。This is something I should have liked to ask you.这是我本来想问你的。这是我本来想问你的。结论：从以上例句可以看出：情态动词结论：从以上例句可以看出：情态动词should用于第一人称时可以表示说话人的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。一种谦逊、客气、委婉的语气。ShouldShould还可以用在还可以用在ifif引导的条件从句，表示引导的条件从句，表示一件事听起来可能性很小，但也不是完全没一件事听起来可能性很小，但也不是完全没有可能。相当于有可能。相当于“万一万一”的意思。从句谓语的意思。从句谓语由由shouldshould加动词原形构成，主句谓语却不一加动词原形构成，主句谓语却不一定用虚拟语气。定用虚拟语气。Ask her to ring me up if you should see her.你万一见到她，请让她给我打个电话。你万一见到她，请让她给我打个电话。If you should change your mind,please let us know.万一你改变主意，请通知我们。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。万一我明天有时间，我就来。此外，此外，Why(or How)+shouldWhy(or How)+should结构表示说话结构表示说话人对某事不能理解，感到意外、惊异等意思。人对某事不能理解，感到意外、惊异等意思。意为意为“竟会竟会”。Why should you be so late today?你今你今天怎么来得这么晚？天怎么来得这么晚？Where is Betty living?How should I know?I dont know why you should think that I did it.我真不知道你凭什么认为这件事是我真不知道你凭什么认为这件事是我干的。我干的。注意：注意：1“should+have+过去分词过去分词”结构结构一般表示义务，表示应该做到而实际上没有一般表示义务，表示应该做到而实际上没有做到，并包含一种埋怨、责备的口气。如：做到，并包含一种埋怨、责备的口气。如：She should have finished it.I should have helped her,but I never could.You should have started earlier.6.will和和would的用法的用法(1)表示请求、建议等，表示请求、建议等，would比比will委婉委婉客气。如：客气。如：Would you pass me the book?(3)用用“will be”和和“will(would)+have+过去分词过去分词”的结构表示推测，主要用于第二、的结构表示推测，主要用于第二、三人称。前者表示对目前情况的推测，后者三人称。前者表示对目前情况的推测，后者表示对已经完成的动作或事态的推测。如：表示对已经完成的动作或事态的推测。如：This will be the book you want.He will have arrived by now.(2)表示意志、愿望和决心。如：表示意志、愿望和决心。如：I will never do that again.They asked if we would do that again.The guests would have arrived by that time.I thought you would have finished this by now.The wound would not heal.During the vacation he would visit me every week.(4)Would可表示过去反复发生的动作或可表示过去反复发生的动作或某中倾向。某中倾向。Would表过去习惯时比表过去习惯时比used to正式，并没有正式，并没有“现已无此习惯现已无此习惯”的含义。的含义。如：如：(5)表料想或猜想。如：表料想或猜想。如：It would be about ten when he left home.What would she be doing there?I thought he would have told you all about it.7.ought to的用法的用法(1)Ought to表示应该。如：表示应该。如：You ought to take care of him.(2)表示推测。注意与表示推测。注意与must表示推测时的区别：表示推测时的区别：He must be at home by now.（断定他已到家）（断定他已到家）He ought to be home by now.（不十分肯定（不十分肯定This is where the oil must be.（比较直率）（比较直率）This is where the oil ought to be.（比较含蓄）（比较含蓄）“ought to+have+过去分词过去分词”表示过去应表示过去应做某事而实际未做。如：做某事而实际未做。如：You ought to have asked him(but you didnt).这时，这时，ought to和和should可以互相换用。可以互相换用。注意：在美国英语中，注意：在美国英语中，ought to用于否定句和用于否定句和疑问句时，疑问句时，to可以省略。可以省略。Ought you smoke so much?You oughtnt smoke so much.8.used to，had better，would rather的用法的用法1Had better意为意为“最好最好”，后接不带，后接不带to的的不定式。如：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，（用于进行时态，表表“最好立即最好立即”）You had better have done that.（用于完成时（用于完成时态，表未完成动作）态，表未完成动作）exit