高中英语情态动词讲义

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1、情态动词情态动词也称为情态助动词, 除了帮助句子中的谓语动词构成否定/疑问时态/语态等, 自生还有其基本词义. 表示说话人的需要、猜测、意愿或怀疑等.一、情态动词的特征 1. 情态动词没有人称和数的变化,即情态动词第三人称单数不加- s (have to, have got to, be able to 除外)。2. 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。3. 情态动词是互相排斥的，一般不允许两个意义相近的情态动词连用。【误】Can I be able to borrow two books at a time?【正】Can I borrow two books

2、 at a time? 我能一次借两本书吗？【正】Will I be able to borrow two books at a time? 我能一次借两本书吗？二、情态动词的意义和用法(请求许可/推测可能/能力才能/要求建议/意志决心)(一)请求许可Can/could/may/might1. can/couldcan: 表示说话人和一般的许可，用于肯定句和否定句，也可以用于疑问句中, cannot 表示“禁止”, 但在正式场合下不能使用（文书/公告）。could主要用于疑问句，比用can更加迟疑不决,当没有把握得到允许时,这样更婉转。答语要用can. e.g. Can I go with y

3、ou? -Could I use your phone?-Yes, of course you can. You cannot smoke in the office. These days children can do whatever they want.2. may/might同can相比, may和might用于比较正式文体，往往含有尊敬之意。用于肯定，疑问和否定句。May not用于拒绝给予许可，或禁止做某事,通常在正式的官方公告中.might 表示比较迟疑，婉转。用于非常正式的场合，不很常用, 在给予被人许可时常用can,有时也用may, 但不能用might.e.g. May I

4、 come in please? I wonder if I might speak to your son. -May I turn on the CD player? - No, you may not/ cannot/ No, you mustnt. （具有强烈禁止的意思）(不可说：No, you might not) Any book may not be taken out of the library. Cars may not be parked in front of the hall.总结：表示请求许可是can/could/may/might礼貌程度依次递增. 肯定回答常用：

5、Yes, you can/may. 否定回答常用：Sorry, I am afraid not. 或Id rather you didnt或 No, you may not/cannot.3. must : 一般用于否定句。must not比may not更为强调。e.g. You mustnt play football in the street, children.4. shall: 一般用于第一，三人称疑问句中e.g. Shall I open the window? Shall he come to see you? 肯定回答,一般是of course； certainly；yes,

6、 please。否定回答，一般是no, thanks。5. will/would: 一般用于第二人称, would 更客气。e.g. Will/Would you spell your name?(二) 推测可能1. can/could: 1)表示逻辑上或理论上的普遍的或者偶尔的可能性，而不是某种实际上将要发生或正在发生的可能性，并非说话人的主观猜测。e.g. Anybody can make mistake. （普遍性）The weather here could be very cold in winter. （偶尔的）2) 说话人主观的猜测“可能”，多于be连用。多用于疑问句或否定句中。

7、Can和could 没有事态的差别，只是could 不太肯定。e.g He cant be at home. Can the news be true?注意：不表示某事实际发生的可能 e.g. It can rain this evening. (误)2. may/might表示事实上的可能, 某事未来或正在可能要发生。might表示的可能性比may小一些。一般用于肯定和否定陈述句：May+ do/be doinge.g. It may/might rain tomorrow. 明天可能下雨。 Lets speed up. They may/might be waiting for us no

8、w.注意: 和can not 的区别: (may not: 可能不；cannot: 不可能)e.g. He cant be at home.他不可能在家。He may not be at home. 他可能不在家。用法比较：might/may/could/can表示可能性时的从小到大 e.g. You might/may/could/can be right. (可能性：30%-40%-50%-60%)3. must: 一般用于肯定句, 否定句或疑问句中用can代替（cannot/Can?）1)表示说话人的对现在/正在进行/将来的动作或状态非常肯定的有根据的推测。Must+ do/be doi

9、nge.g. You must be ill. I can see it form your face. Something must be burning. I can smell it. Bell must be leaving tomorrow.2)表示根据逻辑必须发生的事。e.g. All men must die. 人都是要死的。 Winter must be followed by spring. 冬天到了，春天还会远吗？4will/would1)表示说话人对将来和现在的预测。e.g. I think he will/would be all right now. 我想他现在一定好

10、了。2)有时表示某种倾向和习惯性。Would do 可表示过去常常。e.g. Oil will float on water. 油浮在水面上。 Why dont you put the meat in the refrigerator? It will stay fresh for several days. He would get up very early. 过去他常常起的很早5. ought to：一般用于肯定。e.g.They ought to be there by now. 他们现在一定到那了. They ought to win- they have trained hard

11、enough. 他们应该能赢，他们训练的够苦的。6shall/should：表示说话人的猜测，多指预期的事，表示：估计应该/按道理应该。e.g. I shall be rich one day. 总有天我会发财的。 That should be Janet coming upstairs now. 正在上楼的准是珍妮特。 （三）能力才能can/could/be able to: 表示人或动物的内在能力。有某种知识或者技能而能够做某事。用于肯定，否定和疑问句。e.g. He can/is able to speak two foreign languages.注意：can与be able to

12、用法上的区别：1. can只有两种时态, 即can 和could； 而be able to 有将来式，完成式等多种时态。但二者均无进行时态。e.g. Ill be able to drive the car in a week. Tom has been able to drive.2表示过去通过努力终于做成了某事要用be able to，而不能用can。如：E. g. I was able to swim to the bank after the boat turned over.3. can 是情态动词，只能用作谓语成分，be able to是普通动词短语，既可以作谓语，也可以作非谓语。

13、如：e.g. Being able to speak English fluently, he has no difficulty in communicating with the Americans at the party.4. be able to 后边接动词不定式表示一种实际情况时，其否定形式不是be not able to，而是cannot。如：e.g. -Were you able to catch the first bus yesterday morning?-No, I couldnt.5. 一般说来, be able to 后边的动词不定式没有被动语态。如:e.g. Im

14、 sure he is able to correct his mistakes in grammar.不说: *Im sure his mistakes are able to be corrected by him.6Be able to 前面可以加can以外的情态动词。E.g. You might be able to persuade him.I ought to be able to live on my salary.7. could经常和动词see, hear, smell, taste, feel, remember, understand等连用。不用was able to e

15、.g. When we went into the house, we could smell something burning. She spoke in a very low voice, but I could understand what she said.8. 在谈论说话时发生的动作，用can，不用be able to。 【误】Look! Im able to swim. 【正】Look! I can swim. 看，我会游泳了！ (四) 要求建议1. must: 1) 用于肯定句，表示说话人的意志和义务。或要求对方必须作某事。2) 疑问句用于征求说话人的意见。肯定回答用：Yes

16、, you must. 否定用neednt 或dont have to - Must I finish my homework today?- Yes, you must./ No, you neednt./No, you dont have to.2. may/might1) may 用于法律和条约，相当于shall。用的较少。e.g. A civil juristic act may be in written, oral or other form.民事法律行为可以采取书面形式、口头形式或者其他形式(中华人民共和国民法通则第56 条)。2) might用来对人们提出建议, 可以用来提出批

17、评, 不能与may替换。e.g. You might have considered your parentsfeelings.3. Shall/shouldShall:1) 用于第二/第三人称作主语的陈述句中，表示给对方的许诺, 命令，警告，威胁。E.g. You shall get an answer from me tomorrow.The children shall get a gift if they are nice.You shall be punished for what you have done.2) 用于第三人称作主语的陈述句中，在条约，规定，法令等文件中表示义务和规

18、定，表示“应该， 必须”e.g. All payment shall be made in cash. Those belonging to our school shall wear uniform.Should: 表示义务，责任，提出建议e.g. Todays children should learn to respect their elders. We should take good care of the little kids. Should I help you with the community affairs?3) Ought to ought to 强调在客观上（法律

19、，章程和道义）(或者是自己的意见听上去像法律和义务一样有力), 比should语气强。e.g. You ought to go and see Mary tomorrow.明天你应该去看玛丽。 We ought to defend our country. 我们应当保卫我们的国家。（每一个公民应尽的义务）(五) 意志决心will/would：可表示意志、愿望和决心，用于各种人称陈述句。will表示意愿或决心时，可用于条件状语从句。e.g. e.g.I will do anything for you. I will never tell you the secret. They would n

20、ot let him in because he was poorly dressed. If you will give up smoking, your health will improve.如果你愿意把烟戒掉的话，你的健康状况就会好转。三情态动词特殊用法1.May+主语+动词原形表示祝愿。 e.g. May you succeed. 祝你成功 May that day come soon.希望这一天早日到来。2must有时可用来表示“偏要/非得”的意思。 e.g. Why must it rain today? 为什么偏偏在今天下雨？ When I was taking a nap,

21、a student must knock at the door.正当我午睡时，偏偏一个学生在这个时候来敲门。3. should表示说话人的惊奇，愤怒，失望的特殊情感, 意为：居然/竟然 e.g. How should I know where youve left your bag? I am surprised that you should talk with me like that.4. can用在否定句和疑问句中表示惊讶。 e.g. How can such a simple meal costs so much? This cannot done by him.四情态动词的习惯用

22、法：1Can的习惯用法：1) cannot help doing sth: 情不自禁2) can but do: 只好3) cannot (help) but do sth: 不得不4) can not/can never too: 无论也不过分e.g.I cannot help thinking of him when I am lonely. We can but do our best.The girl cannot (help) but live on herself.You can never do the work too well.2. may的习惯用法： 1) may (mig

23、ht) well: 很可能2) may (might) as well:最好，倒不如3. may/mightbut: 我承认是事实，但是e.g. He may/might well be in the house. 他很可能在房子里。 There is nothing to do, so I may/might as well go to bed. It may rain tomorrow, but weve been determined.4dare的习惯用法：1)I dare say: 表示猜测，意为：我相信，我认为，很可能2) How dare you/he/she/they: 你怎么敢

24、？E.g. I dare say you are right. How dare you come in without knocking the door?五情态动词+ be doing: 推测现在正在发生或存在的状态。1) must+ be doing: 用于肯定句中，表示“一定正在”2) Can/cant + be doing：用于疑问句/肯定句中，表示“可能正在吗？/不会正在 ”3) Could + be doing: 用于疑问句/否定句/肯定句中, might肯定程度稍低 ,表示“可能正在”4) may /might be + doing: 用于肯定句中，表示“可能正在”e.g. H

25、e must be doing his homework now. Can she be still working？ He cannot be still working There is no student in the classroom. They could be playing in the playground. She may/might be writing a letter to her parents now.六情态动词+have done, 这种结构有两个主要的用法。(一)表示对过去发生的动作或状态的推测或估计1) must have done: 表示“一定/准是”

26、只用于肯定句2) may/might have done 表示“大概已经” 3) Can/Could have done 表示“可能已经了吗?” 用于疑问句。 4) cant/couldnt have done表示对事情真实性不相信 “不可能吧” could not 更委婉些。e.g. The streets are wet. The street must have rained. They may/ might have taken a later train.I dont know why she didnt call me yesterday. Can (Could) she have

27、 forgotten my telephone number?He cannot/couldnt have gone home because I saw him on the playground just now.(二) 虚拟过去， 表示后悔/惋惜等感情1) could have done 表示“本可以 通常用于肯定句。 2) might have done 表示“本可以 通常用于肯定句 3) neednt have done表示“本没有必要”只用于否定句。 4) darent have done 表示做了原本不敢做的事，只用于否定句。 5) should/ought to have do

28、ne表示“本该”。用ought to责怪语气更强烈。6) shouldnt/ oughtnt have done 表示“本不该做却做了”。用ought to责怪语气更强烈。e.g. We could have walked to the station. It was too near. You might have told him earlier. He is angry now. You neednt have waited for me. He didnt pass the exam. He darent have gone home. You should (ought to) have been here ten minutes ago. I felt vey hot. I shouldnt (oughtnt) have worn the overcoat.