情态动词.docx

1、情态动词情态动词一、概 说情态动词又称为情态助动词，是助动词的一种。助动词(auxiliary)主要有两类：基本助动词(primary auxiliary)和情态助动词(modal auxiliary)。基本助动词有三个：do, have和be；情态助动词有十三个：may, might; can, could; will, would; shall, should; must, need, dare, used to, ought to. 上述两类助动词的共同特征是，能够与实义动词构成谓语或非谓语动词词组：1） 构成否定式：He didnt go and neither did she.The

2、 meeting might not start until 5 oclock.2） 构成疑问式或反义疑问式：Must you leave right now?You have been learning French for 5 years, havent you?3） 构成修辞倒装：Nowhere can he obtain any information about his sister.Hardly had he arrived when she started complaining.4） 代替动词词组：A: Who can solve this crossword puzzle?B

3、: Tom can.A: Shall I write to him?B: Yes, you do.二、情态助动词的特征基本助动词与情态助动词最主要的区别之一是，基本助动词本身没有词义，而情态助动词则有自己的词义，能表示说话人对有关动作或状态的看法，或表示主观设想：What have you been doing since? （构成完成进行体，本身无词义）I am afraid I must be going. （一定要）You may have read some account of the matter. （或许已经）除此之外，情态助动词还有如下词法和句法特征：1） 除ought和use

4、d以外，其他情态动词后面只能接不带to的不定式。如果我们把ought to和used to看作是固定词组的话，那么，所有情态动词无一例外地只能接不带to的不定式：We used to grow beautiful roses.I asked if he would come and repair my television set.2） 情态助动词在构成动词词组时总是位居第一：They need not have been punished so severely.3） 情态动词不随人称和数的变化而变化（即不管是何人称，后面的情态动词都一样不变），具体说来就是情态助动词用于第三人称单数现在时的

5、时候，没有词形变化，即其词尾无-s形式：She dare not say what she thinks.4）情态动词没有非谓语形式，即没有不定式、-ing分词和-ed分词形式：Still, she neednt have run away.5） 情态助动词的“时”的形式并不是时间区别的主要标志。在不少场合，情态助动词的现在时和过去时形式都可以表示现在、过去或将来时间：Would you mind very much if I ask you to do something?She told him he ought not to have done it.6） 情态助动词之间是相互排斥的，即

6、在一个限定动词词组中只能出现一个情态助动词，但有时却可以与have和be基本助动词连用：You should have washed the wound.Well, you shouldnt be reading a novel.三、情态动词的具体用法can 与 could表示能力（过去的能力用could）Two eyes can see more than one.The theater can seat 2,500 people.Can you lift this heavy box? /Could you follow her talk?I couldnt understand what

7、 he said at all.比较can 和be able tocan、could 表示能力，可能 (过去时用could), 只用于现在式和过去式(could)。be able to可以用于各种时态, 其后的动词不定式只能用主动语态。They will be able to tell you the news soon. 他很快就能告诉你消息了。2）只用be able to 的情况 a. 位于助动词后。He has been able to swim. b. 情态动词后。He must have been able to swim by last year. c. 用于句首表示条件。Able

8、 to swim, we may save ourselves in danger. d. 表示成功地做了某事时，只能用was/were able to， 不能用could。He was able to flee Europe before the war broke out.= He managed to flee Europe before the war broke out.例题：He was a good swimmer, so he _ swim to the river bank when the boat sank. A. could B. might C. shall D. w

9、as able to答案选D，表示成功地游到了对岸。表示许可、允许（和may意思相近，在口语中更常用，may 比较正式） You can go now. This sort of things cant be done. You can use a different material instead. He said I could borrow his bike. She asked whether she could take the books out of the room.* 在日常交际中，提出委婉的请求，could 可用于更加委婉地表示请求，不一定用于过去式。（注意在回答中不可用

10、could）。 Could/ Can you lend me your thermos? - Could I have the television on? - Yes, you can. / No, you cant.表示惊异、怀疑、不相信等态度（主要用在否定句、疑问句、或表示惊叹的句子中），此时could不表示时态, 在口气上比较缓和，用can时，不相信的程度较大。 He couldnt be a bad man.他不大可能是坏人。 What on earth can this mean? Oh, that cant be true. How can/could you be so car

11、eless! Where could/can they be now? He couldnt/cant be over fifty.4. can/could 与have done连用 1）用于表示对过去的猜测，对过去发生的行为的怀疑或不肯定，主要用在疑问句或否定句中：(用could语气更加委婉) He cant have been to that town. Can he have got the book? They can/could not have gone to the hospital. 他们不可能已经到医院去了。2) could have done 常用在肯定句中，用来表示事实上

12、没有实现的行为，有时带有说话人比较缓和的责备语气，译为“本来能够”。You could have come here early. 你本来可以早点到这儿来的。You could have finished it earlier. 你本来能早点完成这件事的。He could have finished the task on time, but the heavy snow came. 偶尔出现在否定句中，表示本来不能做到，但实际上已做了。She could not have covered the whole distance, but in fact she arrived ahead of

13、 time.may与might 表示请求、许可，询问一件事可不可以做或允许可以做的事，过去的请求许可用might；而在现在时态中用might比may的语气更委婉一些且might含有比较迟疑或缺乏自信之意。否定回答时要用mustnt表示“不可以”、“禁止”、“阻止”之意。May/Might I trouble you with a question? Might I ask for a photograph of Mr. Wu? （比may更加客气） 注：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。在日常口语中，用Can I . 征询对方意见在现代口语中更为常见。You m

14、ay take this seat if you like. You may go now.You may take the boy there.He told me I might come. (过去时态，might与told相呼应)He asked if he might come in.She suggested a few books which I might buy.She was afraid they might not like the idea.注意答语：May I smoke here? - Yes, you may. (此种口气显得较为严肃正式，不能用might) -Y

15、es, please./Certainly.（常见回答） -No, you mustnt. (语气强硬) / Please dont.(较为客气) / Youd better not.成语： may/might as well，后面接不带to 的不定式，意为不妨。 If that is the case, we may as well try.You might as well speak your mind.你不妨把心里话说出来。(might比may 更为婉转)用于目的状语中。The emperor gave them some gold in order that they might b

16、egin their work at once.表示可能性，说明一件事或许会发生（或某种情况可能会存在），否定句中译成“可能不/或许不”（might的可能性较弱）。You may walk ten miles without seeing a house.She may not be there today.We may get a new computer in the summer.You might have some fever. 你或许有点发烧。(现在的可能性，比may小一些)Now he might know her address. Be careful, or you migh

17、t break it. 小心点，要不你可能会将它弄破的。典型例题Peter _come with us tonight, but he isnt very sure yet. A. mustB. may C. can D. will答案B. 表可能性只能用may.此句意可从后半句推出。may/might与have done连用表示对过去事情的猜测，认为某事可能发生。He may /might have played electric game on TV the whole night. (for he looks very sleepy.)他可能玩了一夜的电子游戏。（因为看上去很困。）You

18、 may have read the book.He may not have told you about it. 他也许没有告诉你那件事。might与have done连用，在肯定句中，可用于表示事实上没能实现的行为，主要出现在虚拟的条件状语从句中。She might have missed the bus, if she hadnt got up early.If he had been here, you might have got some help from him.may 表示“祝愿”，用在倒装句中。May you succeed! (=I wish you success.)

19、May you have a good time！must 表示必须要做的事。否定句中表示“禁止”。Soldier must obey orders.We must do everything step by step.You mustnt talk like that. (你可不能这样说话。)We mustnt stay here any longer. 在回答由must引起的问题时，如果是否定的答复，常用neednt或dont have to-Must we hand in our exercise books today?-Yes, you must. No, you dont have

20、 to./ No, you neednt.比较have to和mustmust无过去式，但可用在间接引语中或宾语从句中表示过去的情况，have to 可用在各种时态。have to有人称、数、时态的变化，而must只有一种形式He told me I must do according to what he said.He told me I must be there at five.I felt I must call and see them. He had to look after his sister yesterday.-Its raining heavily; we cant

21、go now.-I think well have to wait till the rain stops.must强调主观看法，have to 则侧重客观需要,如：The play is not interesting. I really must go now.I have to work when I was your age.My brother was very ill, so I had to call the doctor in the middle of the night.我弟弟病得很厉害，我只得半夜里把医生请来。(客观上需要做这件事)He said that they mu

22、st work hard. 他说他们必须努力工作。（主观上要做这件事）二者的否定意义大不相同。dont have to 表示不必mustnt表示禁止，You mustnt go. 你不能去。You dont have to go. 你不必去。You dont have to tell him about it. 你不一定要把此事告诉他。You mustnt tell him about it.你一定不要把这件事告诉他。询问对方意愿时，应用must。Must I clean all the room? 需要我清洗所有的房间吗？表示一种揣测，只用于肯定句中，否定句中用can代替must。1) mu

23、st用在肯定句中表示较有把握的推测，意为一定。2) must表对现在的状态或现在正发生的事情的推测时， must 后面通常接系动词be的原形或实义动词的进行式。 You have worked hard all day. You must be tired. 你辛苦干一整天，一定累了。（对现在情况的推测判断）He must be working in his office. 他一定在办公室工作呢。比较： He must be staying there. 他现在肯定呆在那里。 He must stay there. 他必须呆在那。 3) must 表示对已发生的事情的推测时，要接完成式。 I

24、didnt hear the phone. I must have been asleep.我刚才没有听到电话，我想必是睡着了。4) must表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。 -Why didnt you answer my phone call? -Well, I must have been sleeping, so I didnt hear it.5) 否定推测用cant。 If Tom didnt leave here until five oclock, he cant be home yet.如果汤姆五点才离开这儿，他此时一定还未到家。6)

25、注意反意疑问句的形式，一般跟must后的动词形式一致， He must be in the classroom, isnt he? The room must have been cleaned by Li Ping, hasnt it? He must have left Shanghai yesterday, didnt he? (含过去的时间状语时，用过去式)need 与dare用法相似，意义不同；都可既作情态动词又作实义动词，need表示需要，dare表示敢于；2、 need表示“需要”或“必须”，作情态动词时，仅用于否定句或疑问句中，在肯定句中一般用must, have to, ou

26、ght to,或should代替。如： You neednt come so early. Need I finish the work today? Yes, you must. 注意：neednt + have done表示“本来不必做某事而实际上做了某事”。区别did not need to do，表示“不必做，实际上也没做”。如： You neednt have waited for me.你其实不必等我。（实际上等了） I didnt need to go to work yesterday, so I went fishing.3、 Dare作情态动词时，主要用于疑问句、否定句和感

27、叹句中，一般不用在肯定句中(注：情态动词dare有过去式dared)。如： How dare you say Im unfair! He darent speak English before such a crowd, dare he?4、Dare和need常用作实义动词，加带to 的不定式，用于各种句式，有时态、人称和数的变化。He needs to go. / He doesnt need to go.Does he need to do it again? No, he doesnt need to do it again. 注：need doing以主动形式表示被动意义，相当于nee

28、d to be doneMy radio needs repairing/ to be repaired.He dares to say. / He doesnt dare (to) say.If you dare to jump into the water from here, so dare I. (前为实义动词，后为情态动词。)注：在肯定句中，dare后面通常接带to的不定式，在否定和疑问句中，dare后面可接带to或不带to的不定式。如：I dare to swim across this river.He does not dare (to) answer.Dont you dar

29、e (to) touch it!I wondered he dares (to) say that.He needs to finish it this evening.will与would 1、表示请求、建议等，would比will委婉客气。如：Would you pass me the book?注意：1）would like；would like to do = want to 想要，为固定搭配。 Would you like to go with me?2）Will you?Would you like? 表示肯定含义的请求劝说时，疑问句中一般用some, 而不是any。 Would

30、you like some cake?3）否定结构中用will，一般不用would，wont you是一种委婉语气。 Wont you sit down？2、表示意志、愿望和决心。如： I will never do that again. They asked if we would do that again.3、will可表示惯性动作“总是、惯于”；(动作的趋势)Fish will die without water.The radio wont work.Whats the matter with the door? It wont lock.4、用“will be/do”和“will

31、/would + have + 过去分词”的结构表示推测，主要用于第二、三人称。前者表示对目前或将来情况的肯定的推测，后者表示对将来一个时间之前已经完成的动作或事态的推测（将来完成时）。如： This will be the book you want. He will have arrived by tomorrow. The guests would have arrived by that time. I thought you would have finished this by now.5、比较used to与would1）used to表示过去的动作状态,重在与现在情况的对比,不一定要有时间状语；would 只表示过去动作的重复，有明确的时间状语；I used to play cards