情态动词及虚拟语气讲解

1、精选优质文档-倾情为你奉上情态动词结构图 概述 can和could的用法 may和 might的用法must的用法 need和dare的用法情态动词 基本用法 shall和 should的用法 will和 would的用法 ought to的用法used to的用法 had better与would rather的用法 情态动词must, can, could, may, might 其它用法 表推测的用法 “情态动词+have+done” 结构的含义及用法一、概述：情态动词有：can(could)，may(might)，must(must)，have to，shall(should)，wil

2、l(would)，need(need)，dare(dared)，ought to.情态动词无人称和数的变化，不能独立使用它与其后边的动词原形一起构成谓语情态动词的具体用法如下:    二、情态动词的用法：(一) can和could的用法    l. 注意can和could的一般疑问句的回答（could用在疑问句中比can语气更委婉）。如:Can you finish this work tonight?-Yes，I can./No，I can't.Could you help me-Sure./Certainly./OK.？O

3、f course.或Yes，I can. /No（或Sorry），Im afraid not.    2. can和could表示推测（见后面）。3. can与be able to的区别：can常常指某人具备某种知识或技能，而be able to则指具体做某件事的能力。如：I can read，but I am not able to read this passage.can常常只有现在或过去两种形式，而be able to可以有多种形式，可以用于多种时态。如：Jim can read and write now，but he couldnt do it whe

4、n he was four years old.At that time he was able to answer the question，now he is able to answer the question too. Of course he will be able to answer such question easily in the future.(二) may和 might的用法    1注意may与might的一般疑问句的回答（might用在疑问句中比may语气更委婉）。用May I征询对方许可在文体上比较正式，在口气上比较客气。在日常口

5、语中，用 Can I征询对方意见在现代口语中更为常见。如: May/Might I ask you some questions？ -Yes，you may./Yes，you can./Yes，you must./Yes，please.-No，you may not.（一般不常用）/No，you can't./No，you mustn't./No，you'd better not.2. may和might表示推测（见后面）。    3. 用于祈使句中表示祝愿例如： May you succeed!(三) must的用法：1.注意m

6、ust的一般疑问句的回答：Must I go there at once？-Yes，you must./No，you needn't.=No，you dont have to.     2.must表示推测（见后面）。3.must与have to的区别： must只有一种形式，而have to有各种形式和时态，随 have的变化而定。must表示的是说话人的主观看法，而have to则往往强调客观需要例如：     The play is not interesting. I really must go now.

7、I have missed the bus，so I have to walk home. I had to work when I was your age.    (四) need和dare的用法    1作情态动词：need表示“需要”或“必须”，仅用于否定句或疑问句中，在肯定句中一般用 must，have to，ought to，或 should代替（注意其一般疑问句的回答方式与must完全一样）；dare主要用于疑问句、否定句和条件状语从句中，一般不用于肯定句。例如：    You neednt

8、 come so early.    Need I finish her work today? -Yes，you must./No，you needn't.=No，you dont have to.Dare he do it？-No，he darent. How dare you say Im unfair If you dare come here，I will come to meet you. He darent speak English before such a crowd，dare he?-Yes，he dare./No，he darent

9、.注意：neednt have done“表示本来不必做某事而实际上却做了某事”。例如：    You neednt have waited for me  2. 作实义动词：dare和 need后面接不定式（to do），有人称、数和时态的变化，变否定句和疑问句时要借助于助动词。所不同的是，作实义动词时，在肯定句中，dare后面通常接带 to的不定式；而在否定和疑问句中，dare后面的不定式可以不带to例如：    I dare to swim across this river.    He

10、 does not dare (to) answer.    Dont you dare (to) touch it!    I wondered he dare (to) say that    Does he dare to go there？-Yes，he does./No，he doesnt. He needs to finish it this evening  He doesnt need to finish it this evening. Does he need to fini

11、sh it this evening？-Yes，he does./No，he doesnt.   (五) shall和 should的用法 。1.Shall的用法：shall用于第一人称的肯定句表示将来，用于第一人称的特殊疑问句表示征求对方的意愿例如：I shall go to Beijing tomorrow. What shall we do this evening?    shall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提出请示。例如：Shall we begin our lesson? When sha

12、ll he be able to leave the hospital?    shall用于第二、三人称的肯定句中，表示说话人给对方的命令、警告、允诺或威肋例如：You shall fail if you dont work harder(警告) He shall have the book when I finish reading(允诺)He shall be punished.(威胁)    2. should的用法：should的用法：a. should表示劝告、建议、命令，其同义词是ought to如： You

13、should go to class right away. Should I open the window?    b.should可以用在if引导的条件从句中，表示一件事听起来可能性很小,但也不是完全没有可能。相当于“万一”的意思。从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气。例如：    Ask her to ring me up if you should see her.你万一见到她，请让她绘我打个电话。    If you should change your mind，

14、please let us know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。    c.“Why/How should？”结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会”。例如：Why should you be so late today?你今天怎么来得这么晚? Where is Betty living? 一How I should know?    - 贝蒂住

15、在哪里?    - 我怎么会知道呢?    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干的。    d.“ should have done”表示本应该做到而实际上没有做到    You should have started earlier.    ought to的用法：a.ought to也表示“应该”，注意其肯定句、否定句、一般疑问句及回答。You oug

16、ht to obey the law.-You oughtn't to obey the law. Ought you to obey the law？-Yes，I ought to./No，I oughtn't to.b.“ought to have done”表示（按规则）过去应做某事而实际未做例如： You ought to have helped him( but you didnt).    这时，ought to与 should可以互相换用 注意，在美国英语中，ought to用于否定和疑问句时，to可以省略例如:&

17、#160;   Ought you smoke so much? You oughtnt smoke so muchshould与ought to的区别。should侧重表示道德上理应如此，而ought to侧重表示在规则、条例或法律上应该如此。如：You should go to class right away. According to the law you ought to obey the rules.(六) will和 would的用法    1.will的用法：will表示请求、建议等。例如： Will/Would y

18、ou pass me the book?    表示意志、愿望和决心。例如： I will never do that again They asked as if we would do that again.2.would的用法：would是will的过去式。注意其两种固定问句的回答方式。Would you like？-Yes，please./No，thanks.Would you like to do？-Yes，I'd love to./I'd love to，but./I'm sorry I can't.would

19、与used to的区别：would表示过去反复发生的动作，没有“现已无此习惯”的含义；而used to表示过去反复发生的动作或某种倾向，有“现已无此习惯”的含义。例如：    He used to come here early，but now he doesnt do it. He said he would write many novels when he was young. He used to be a teacher，but now he isnt.    3will与would的区别：would比will委婉客气；用“

20、 will be”和“ will have done”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，后者表示对已经完成的动作或事态的推测；而“would be”和would have done表示料想或猜想例如：    This will be the book you want    He will have arrived by now.It would be about ten when he left home    What would she be doing there?&#

21、160;   I thought he would have told you all about it.       (七) ought to的用法1.ought to也表示“应该”，注意其肯定句、否定句、一般疑问句及回答。You ought to obey the law.-You oughtn't to obey the law. Ought you to obey the law？-Yes，I ought to./No，I oughtn't to.2.“ought to have done”

22、表示（按规则）过去应做某事而实际未做例如：You ought to have helped him( but you didnt).    这时，ought to与 should可以互相换用注意，在美国英语中，ought to用于否定和疑问句时，to可以省略例如:    Ought you smoke so much? You oughtnt smoke so much(八) used to的用法    used to表示过去的习惯动作或状态，现在已不存在（would do只能表示过去习惯性的动作而不能表

23、示过去的状态，并且这种动作现在也可能存在），在间接引语中，其形式可不变。注意在疑问句、否定句、否定疑问句或强调句中，可有两种式。例如He told us he used to play football when he was young     疑问句Did you use to go to the same school as your brother?Used you to go to the same school as your brother?     否定句I usednt to go there. 

24、   I didnt use to go there    usedn't亦可拼作 usen't，但发音皆为ju：znt.    否定疑问句Usent you to be interested in the theatre?Didnt you use to be interested in the theatre?    强调句I certainly used to smoke， but it was a long time agoI certainly did use

25、 to smoke , but it was a long time ago     其反意疑问句或简略回答中，也有两种形式：She used to be very fat，didnt she?/use(d) nt she?Did you use to play chess? Yes，I did.Used you to get up early in the morning? Yes, I did./Yes, I used to.    （九）had better与would rather的用法：1.had better 意为“最好”

26、，后接不带 to的不定式。例如:-We had better go now.-Yes，we had ( we'd betterwe better had?)Hadnt we better stop now?  (Had we better not stop now?)I think Id better be going.(用于进行时态，表“最好立即”)You had better have done that.(用于完成时态，表未完成动作)    注： had best与 had better同意，但较少用。   

27、You had better 用于同辈或小辈，对长辈不可用    2.would rather意为“宁愿”，表选择，后接不带 to的不定式。例如：  Id rather not say anythingWould you rather work on a farm? -Wouldnt you rather stay here?    - No，I would not，I'd rather go there    由于 would rather表选择, 因而后面可接 than.

28、例如:I would rather work on a farm than in a factoryI would rather watch TV than go to see the filmI would rather lose a dozen cherry trees than that you should tell me one lieId rather you didnt talk about this to anyone(句中的d rather不是情态动词，would在此是表愿望的实义动词)。附：情态动词表示推测及“情态动词+have+done” 结构分析一、情态动词must,

29、can, could, may, might表推测的用法：情态动词中的must, can, could, may, might都表推测。其中must的可能性最大，can / could次之，may / might最小。具体用法如下：1.它们出现的句型不同：must常用于肯定句中表推测，can常用于否定句和疑问句中表推测（也可以用于肯定句中，但不常见），could常用于肯定句、否定句和疑问句中表示推测；may/might常用于肯定句和否定句中表推测（might表推测时比may的可能性更小）。如：He must be a teacher.-He can't be a teacher./Ca

30、n he be a teacher？ The weather can be quite warm in winter. The plane could be delayed by fog. It couldnt possibly be poison. He may/might be a teacher.-He may/might not be a teacher./Can he be a teacher？ You must have been to Shanghai. If you come here earlier yesterday，you could have met him. He c

31、an't/couldn't have been to the town. Can he have been to the town？ Where can (could) they have gone? He may/might have finished the work. He may/might not have finished the work. 2.有两种不同的推测形式：“can/could/may/might/must + be”表示对现在情况的推测，而“can/could，may/might，must+ have done”则表示对过去的推测。must be为“肯

32、定是，一定是”，can't/couldn't be为“不可能是”，may/might be为“可能是”，may/might not be为“可能不是”； must have done“肯定是做过”，can/could not have done“不可能已经做过”，may/might have done“可能已经做过”，may/might not have done“可能没有做过”。例子见上面。3.注意变反义疑问句：如果它们后面接be，表示对现在的推测，变反义疑问句时，应将其当成be动词一般现在时态看待。如：He must be a teacher，isn't he？ H

33、e can't be a teacher，is he？ He may be a teacher，isn't he？ He may not be a teacher，is he？如果它们后面接have done，表示对过去的推测，变反义疑问句时：如果句中有了表示过去的具体的时间状语，应将句子当作实义动词的一般过去时态看待；如果句中没有具体的时间状语，应将句子当作现在完成时态看待。如：Lucy must have gone there yesterday，didn't she？ He must have finished his homework，hasn't he

34、？下面这些短语不具有推测含义：could have done“本来能够做而没有做”，ought to have done“本来应该做而没有做”（表示从客观法律、义务或规则上看应该做而没能做到），should have done“本来应该做而没有做”（表示从主观上看应该做而没能做到），needn't have done“本来不需要做而已经做了”。如：We could have come here an hour earlier. You ought to have finished your homework. You needn't have come here early.

35、4.注意：must表示推测时很少用于将来的情况。一般不用He must come tomorrow.可用Its certain / Im sure that he will come tomorrow. may, might可以推测将来的情况。如：I think we should take raincoat with us, it may rain. 我想我们应该带上雨衣，可能要下雨了。She might not come this afternoon. 她今天下午可能不来了。二、“情态动词+have+done” 结构的含义及用法1、should have done/ should not

36、have done它们分别表示“过去本来应该（已经）（而实际上并没有）”/“过去本不应该（已经）而实际上却已经”如：We should have studied last night, but we went to the concert instead . 我们昨晚本应学习的，但我们却去看音乐会了。（实际上没有学习）If he had joined us , we should have had a more enjoyable time . 如果他加入我们的活动，我们就可以玩得更开心了。（实际上没那么开心，由于他没加入我们的活动）I should have thought of that

37、.这一点我应该想到的。（但实际上没想到）They shouldn't have left so soon . 他们不应当走得那么早。（但实际上还是走了）He shouldn't have said such a thing .他当时不应该说那种话。（但已经说了）在表示推测时，它表示的是“大概已经，或许已经”的意思。如：The train should have already left.火车大概已经开走了。Time is up , you should have finished your exercises . 时间已到，你们可能已经做完作业了。2、would have do

38、ne 它表示的是与过去事实相反之假设的结果，意思是“当时就会了”，而实际上没有。如：I would have helped you if I had known of your difficulties . 要是我当时知道你们的窘境，我就会帮助你了（而实际上没有帮助你）If it hadn't rained yesterday, we would have gone on excursion .假如昨天没下雨，我们就去远足了。（实际上没有去）。在表示推测时，它表示“过去大概是，似乎、可能”如：I suppose the writer would have been about thir

39、ty when he published his first work . 我想这位作家出版第一部作品时，大概是30岁左右。3.must have done它表示“过去一定了”，且结果延续到现在，用于对过去发生的事进行推测。如：No one answers the phone call, they must have already gene out ,没人接电话，他们一定已经出去了。They must have arrived by now.现在他们想必已经到达。You must have known what he wanted .你当时一定知道他要什么。Where is my pen?

40、I must have lost it . 我的钢笔在哪？我肯定把它弄去了。4.cannot have done/couldn't have done这两个形式表示“过去应该不可能做”如，He can not have promised it . 他应该不会答应那种事。John is very clever . He cannot have told his son to do that . 约翰是很聪明的，他应该不会叫他儿子那样做。He couldn't have said such a thing . 他应该不会说出这样的事。5.can't have done它表示

41、"过去不可能做"。如：She can't have gone to school , we have no school today.她不可能到学校去，今天我们学校放假。He can't have finished the work so soon .这项工作他不可能完成得这样快。Jack doesn't work hard at all. He can't have passed this English examination . 杰克学习根本不用功。他不可能通过这次英语考试。6.can (could)have done这种形式只用于疑问句，表示"含疑问语气的推测"。如：Where can (could) they have gone?他们能到哪里去了呢？How could he have forgotten such an important thing?这么重要的事他怎么能忘了呢？He told me he had a meeting to attend in Beijing. Can he have gone to Beijing to attend the meeting?他告诉我说北京有个会议要参加，他会不会已位去了北京呢？Can you hav