1、1第五讲 情态动词一、情 态 动 词 的 定 义情态动词是一种本身有一定的词义，表示说话人的情绪、态度或语气的动词，但不能单独作谓语，只能和其他动词原形构成谓语。We can be there on time tomorrow. 我们明天能按时去那儿。 May I have your name? 我能知道你的名字吗？ Shall we begin now? 我们现在就开始吗？ You must obey the school rules. 你必须遵守校规。 情态动词数量不多，但用途广泛，主要有下列： can (could), may (might), must, need, ought to,
2、 dare (dared), shall (should), will (would) . 二、情 态 动 词 的 位 置情态动词在句中放在谓语动词之前，谓语动词前若有助动词，则在助动词之前，疑问句中， 情态动词放在主语之前。 I can see you. Come here. 我能看见你，过来吧。 He must have been away. 他一定走了。 What can I do for you? 你要什么？ How dare you treat us like that! 你怎么敢那样对待我们! 三、情 态 动 词 的 特 点2情态动词无人称和数的变化，情态动词后面跟的动词需用原形，
3、否定式构成是在情态动词后面加“not” 。个别情态动词有现在式和过去式两种形式，过去式可以用来表达更加客气、委婉的语气，时态性不强，可用于过去，现在或将来。 He could be here soon. 他很快就来。 We cant carry the heavy box. 我们搬不动那箱子。 Im sorry I cant help you. 对不起，我帮不上你。 四、情态动词的语法特征：1） 情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。2） 情态动词 除 ought 和 have 外，后面只能接不带 to 的不定式。3） 情态动词无人称、数的变化，即情态动词第三人
4、称单数不加-s。4） 情态动词没有非谓语形式，即没有不定式，分词等形式。五、情 态 动 词 的 用 法1. can (could) 表示说话人能, 可以, 同意, 准许 , 以及客观条件许可, could 为 can 的过去式。Can you pass me the books? 你能给我递一下书吗 ? Could you help me, please? 请问, 你能帮助我吗? What can you do? 你能干点什么呢? Can you be sure? 你有把握吗? 3can 和 could 只能用于现在式和过去式两种时态，将来时态用 be able to 来表示。 He coul
5、d help us at all. 他完全可以帮助我们。 With the teacher s help, I shall be able to speak English correctly. 有老师的帮助, 我将能准确地讲英语。 2. may (might) “可以” ，表示说话人同意，许可或请求对方许可。 You may take the book home. 你可以把书带回家去。 May I come in? 我可以进来吗? May I use your dictionary? 我可以用你的词典吗? You may put on more clothes. 你可以多穿点衣服。 He s
6、aid he might lend us some money. 他说他可以借给我们一些钱。may 否定式为 may not, 缩写形式是 mayn t。might 是 may 的过去式，有两种用法，一种表示过去式，一种表示虚拟语气，使语气更加委婉、 客气或对可能性的怀疑。 He told me he might be here on time. 他说他能按时间来。 Might I borrow some money now? 我可以借点钱吗? He might be alive. 他可能还活着。3. must “必须；应该；一定；准是” ，表示说话人认为有必要做某事，命令、要求别人做某事以及
7、对事物的推测。must 用来指一般现在时和一般将来时， 过去式可用 have to 的过去式代替。I must finish my work today. 我今天必须完成我的工作。 You mustnt work all the time. 你不能老是工作。 Must I return the book tomorrow? 我必须明天还书吗 ? 4After such a long walk, you must be tired. 走了这么长的路, 你一定累了。 He must be the man I am looking for. 他一定是我要找的人。 He had to go becau
8、se of somebody s calling him that day. 那天他要走，因为有人叫他。值得注意的是：（1）must + have + 过去分词，表示现在对过去事物的推测。 He must have told my parents about it. 他一定把这件事情告诉我父母亲了。He must have received my letter now. 他现在一定收到我的信了。 Its six oclock already, we must have been late again. 已经六点钟了，我们一定又迟到了。（2）must 和 have to 的区别: must 表示
9、说话人的主观思想, have to “不得不,必须” ，表示客观需要、客观条件只能如此。 You must do it now. 你必需现在就干。(说话人认为必须现在干) I have to go now. 我得走了。(客观条件必须现在走)You must be here on time next time. 你下次一定要按时来。I have to cook for my child. 我得给孩子做饭。 4. need “需要” ，多用在否定式或疑问句中. Need I attend the meeting tomorrow? 我需要明天参加会议吗? You need not hand in
10、the paper this week. 这一周你不必交论文。 need 是一个情态动词，他的用法完全和其他情态动词一样，但 need 还可当作实义动词使用，这时 need 就象其他动词一5样，有第三人称，单复数， 后面加带 to 的动词等特性。 I need a bike to go to school. 我上学需要一辆自行车。 Do you need a dictionary? 你需要词典吗? She needs a necklace. 她需要一条项链。 注意：“neednt + have + 过去分词” 表示过去做了没必要做的事情。 You neednt have taken it se
11、riously. 这件事情你不必太认真。 5. dare “敢” ，多用在否定或疑问句中。 The little girl dare not speak in public. 小女孩不敢在公众面前说话。Dare you catch the little cat? 你敢抓小猫吗? dare 除用作情态动词外，更多的是当实义动词使用， 用法同实义动词一样，要考虑人称，单复数，时态等。 Do you dare to walk in the dark? 你敢黑夜走路吗？ He doesnt dare to tell the teacher what happened that day. 他不敢告诉老师
12、那天发生的事。6. ought “应当；应该” ，后面跟带有 to 的动词不定式。 You ought to read these books if you want to know how to repair the motorcar. 如果你想知道如何修理汽车,你应该读这些书。 You ought to bring the child here. 你应该把孩子带来。 ought + to have done 句型。指过去动作,表示一件事情该做而未做。You ought to have been here yesterday. 你昨天就应该来。 ought not to have done
13、句型。表示一件不该做的事情却做了。 6You ought not to have taken the book out of the reading-room. 你不应该把书带出阅览室。7. will (would) 表决心、愿望。 would 为 will 的过去式, 可用于各人称。1）will 表示经常性、习惯性、倾向性， would 表示过去的习惯行为。e.g. a. He will sit there hour after hour looking at the traffic go by. b. He would come to see me when he was in Beiji
14、ng.2）表示意志，决心或愿望。e.g. a. Surely we will support all the people in the world in their struggle for peace.b. He would not let me try it . 3）表示对对方的请求，用于第二人称作主语的疑问句中，would的语气比 will 委碗,疑问句中一般用 some, 而不是 any。e.g. a. would/will you kindly tell me the way to the station?b. Would you like some cake?4）would li
15、ke = want to 想要 Would like to do = want to 想要 e. g. a Would you like to go with me? 8. shall, should 表示命令 , 警告, 允诺, 征求, 劝告, 建议, 惊奇。 shall 的用法用于第一,第三人称征求对方的意愿e.g. a. What shall I wear on the journey? 7b. When shall he be able to leave the hospital? should 的用法1)用于第一人称疑问句中询问对方的意愿，但语气较委婉温和e.g. a. What s
16、hould we do now? 我们现在该怎么办？2)表示应该、必须，常与 must 换用。e.g. a. We should (must) master a foreign language at least. 3).should 表示劝告，建议，命令，此时也可用 ought to. 在疑问句中，通常用 should 代替 ought to.4) should have done 表示过去应该做 而实际没有做 should not have done 表示过去不该做而实际做了9. have tomust1) 两词都是 必须的意思，have to 表示客观的需要， must 表示说话人主观上
17、的看法，既主观上的必要。e.g. a. My brother was very ill, so I had to call the doctor in the middle of the night. (客观上需要做这件事) b. He said that they must work hard. （主观上要做）2) have to 有人称、数、时态的变化，而 must 只有一种形式。但must 可用于间接引语中表示过去的必要或义务。e.g. a. He had to look after his sister yesterday.3） 在否定结构中： don t have to 表示 “不必
18、” mustnt 表示 “禁止”e.g. a. You dont have to tell him about it. b. You mustnt tell him about it. 10.need&dare8这两词既可做实义动词用，又可做情态动词用。作为情态动词，两者都只能用于疑问句，否定句和条件句。 need 作实义动词时后面的不定式必须带 to，而 dare 作实义动词用时 , 后面的 to 时常可以被省略。 1) 实义动词:need+ n. / to do sth2) 情态动词： need，只用原形 need 后加 do，否定形式为 need not。e.g. a. -Need yo
19、u go yet? -Yes, I must.-No, I neednt.3) need 的被动含义：need, want, require, worth（形容词）后面接doing 也可以表示被动： need doing = need to be done11.should 和 ought to 都为“应该”的意思，可用于各种人称。 -Ought he to go?-Yes. I think he ought to.表示要求，命令时，语气由 should（应该） 、had better 最好） 、must（必须）渐强。 12.had better 表示“ 最好“had better 相当于一个
20、助动词，它只有一种形式，它后面要跟动词原形。had better do sth .had better not do It is pretty cold. Youd better put on my coat. Shed better not play with the dog. had better have done sth 表示与事实相反的结果，意为“ 本来最好“。 9You had better have come earlier.六.情态动词的回答方式问句 肯定回答 否定回答Need you?Yes, I must. No,I needn tMust you?Yes, I must.
21、 No, I neednt./dont have to. May I ? Yes, of course. No, you mustnt.Could you? Yes, you can. No, you cant.七.情态动词表猜测must 用于肯定句can 用于否定句或疑问句May 用于肯定句或否定句 should 用于肯定句八.表示推测的用法can, could, may, might, must 皆可表示推测，其用法如下： 1）情态动词+ 动词原形。表示对现在或将来的情况的推测，此时动词通常为系动词。I dont know where she is, she may be in Wuhan
22、. 2）情态动词+ 动词现在进行时。表示对现在或将来正在进行的情况进行推测。At this moment, our teacher must be correcting our exam papers. 10这时，我们老师想必在批改试卷3）情态动词+ 动词完成时。表示对过去情况的推测。We would have finished this work by the end of next December.明年十二月底前我们很可能已完成这项工作了。The road is wet. It must have rained last night.地是湿的，昨天晚上一定下雨了。 4）情态动词+ 动词的
23、现在完成进行时。表示对过去正在发生事情的推测。Your mother must have been looking for you.你妈妈一定一直在找你。5）推测的否定形式，疑问形式用 cant, couldnt 表示。 Mike cant have found his car, for he came to work by bus this morning. 迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。 注意：could, might 表示推测时不表示时态，其推测的程度不如can, may。 九.情态动词+ have + 过去分词1) may(might) have + don
24、e sth, can (could) have + done sth 表示过去，推测过去时间里可能发生的事情。Philip may (might) have been hurt seriously in the car accident.Philip can (could) have been hurt seriously in the car accident.2) must have +done sth，对过去时间里可能发生的事情的推测，语气较强，具有“肯定“ ，“ 谅必“的意思。-Linda has gone to work, but her bicycle is still here.
25、 11-She must have gone by bus.3) ought to have done sth, should have done sth.本应该做某事，而事实上并没有做。否定句表示“不该做某事而做了“。You ought to (should) have been more careful in this experiment. He ought not to have thrown the old clothes away.（事实上已扔了。 ） ought to 在语气上比 should 要强。4) neednt have done sth 本没必要做某事 I dresse
26、d very warmly for the trip, but I neednt have done so. The weather was hot.5) would like to have done sth 本打算做某事 I would like to have read the article, but I was very busy then.十.带 to 的情态动词带 to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to 为六个,它们的疑问，否定形式应予以注意：Do the
27、y have to pay their bill before the end of the month? She didnt use to play tennis before she was fourteen. You ought not to have told her all about it. Ought he to see a heart specialist at once.?例：Tom ought not to _ me your secret, but he meant no harm. A. have told B. tell C. be telling D. having told
