情态动词的概念：

情态动词表示说话人对某一动作或状态的态度。

1、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）情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。
4）情态动词没有非谓语形式，即没有不定式，分词，等形式
2、比较can 和be able to
1）can 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。
   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
　 a. 位于助动词后。
　 b. 情态动词后。
　 c. 表示过去某时刻动作时。
　 d. 用于句首表示条件。
　 e. 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.
注意：could不表示时态
1）提出委婉的请求，（注意在回答中不可用could）。
　 --- Could I have the television on?
　 --- Yes, you can. / No, you can't.
2）在否定，疑问句中表示推测或怀疑。
　 He couldn't be a bad man.　　
　 他不大可能是坏人。
   be able to 表示在特定情景中努力做成某事。 
   The first spread through the building very quickly, but luckily everyone was 
   able to escape.
   大火在楼里蔓延，幸好大家都及时撤离了。（在此不能用could ）
   They didn’t want to come with us at first, but in the end we were able to persuade
   them.
   起初他们不想与我们一起来，但是最后我们还是说服了他们。（在此不能用could）
3、比较may和might
1）表示允许或请求；表示没有把握的推测；may 放在句首，表示祝愿。
　 May God bless you!
　 He might be at home.
   注意：might 表示推测时，不表示时态。只是可能性比may 小。
2）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.
典型例题：
　 Peter ____ come with us tonight, but he isn't very sure yet.
　 A. must　　B. 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。
4、比较have to和must
1）两词都是'必须'的意思，have to 表示客观的需要，must 表示说话人主观上的看法，既主观
   上的必要。
   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 must work hard.
   他说他们必须努力工作。（主观上要做这件事）
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
   去的要或义务。
   He had to look after his sister yesterday.
3）在否定结构中：don’t have to　表示“不必” mustn’t　表示“禁止”，
   You don’t have to tell him about it.　 你不一定要把此事告诉他。
　You mustn’t tell him about it.　　你一定不要把这件事告诉他。
5、must表示推测
1）must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 的原形或行
   为动词的进行式。
　 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，must 要接完成式。
　 I didn't 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 didn't you answer my phone call?
　 ---Well, I must have been sleeping, so I didn't hear it.
5）否定推测用can't。
　 If Tom didn't leave here until five o'clock, he can't be home yet.　
   如果汤姆五点才离开这儿，他此时一定还未到家。
6、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 don't know where she is, she may be in Wuhan.
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.
　 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can't, couldn't表示。
　 Mike can't 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。
7、情态动词+ have +过去分词
1）may(might) have + done 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.
　 ---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）needn't have done sth　本没必要做某事
　 I dressed very warmly for the trip, but I needn't 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 .
8、should 和ought to
   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。
9、had better表示"最好"
   had better 相当于一个助动词，它只有一种形式，它后面要跟动词原形。
   had better do sth
   had better not do sth
   It is pretty cold. You'd better put on my coat.
   She'd 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"。
   You had better have come earlier
10、would rather表示“宁愿”
    would rather do
    would rather not do
    would rather… than…　 宁愿……而不愿。
    还有would sooner, had rather, had sooner都表示"宁愿"、"宁可"的意思。
    If I have a choice, I had sooner not continue my studies at this school.
    I would rather stay here than go home. = I would stay here rather than go home.
典型例题
----Shall we go skating or stay at home?
----Which ___ do?　　　　　
A. do you rather　　B. would you rather　 C. will you rather　 D. should you rather
答案B。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句，would
提前，所以选B
11、will和would
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 you like some cake?
3）否定结构中用will，一般不用would, won't you是一种委婉语气。
   Won't you sit down?
12、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't/don't have to.
Must you…?	Yes, I must.	No, I needn't/don't have to.

典型例题
1）---Could I borrow your dictionary?
　 ---Yes, of course, you____.　
　 A. might　B. will　 C. can　 D. should
　 答案C. could表示委婉的语气，并不为时态。答语中of course，表示肯定的语气，允许某人做
   某事时，用can和 may来表达，不能用could或might。复习： will 与you连用，用来提出要求
   或下命令。should与you 连用，用来提出劝告。
2）---Shall I tell John about it?
　 ---No, you ___. I've told him already.　　
　 A. needn't　　B. wouldn't　　C. mustn't　　D. shouldn't
   答案A。needn't 不必，不用。 wouldn't 将不, 不会的。 mustn't 禁止、不能。 shouldn't
          不应该。本题为不需要，不必的意思，应用needn't。
3）---Don't forget to come to my birthday party tomorrow.
　 ---______.
　 A. I don't　 B.　I won't　 C. I can't　D. I haven't
　 答案B.　will既可当作情态动词，表请求、建议、也可作为实义动词表“意愿、意志、决心”， 
   本题表示决心，选B。
13、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 they have to pay their bill before the end of the month?
    She didn't 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.?
    ought to 本身作为情态动词使用。其他的词作为实义动词使用，变疑问，否定时，须有do
    等助动词协助。
典型例题：
Tom ought not to ___ me your secret, but he meant no harm.　
A. have told　B. tell　C. be telling　D. having told
答案A。由于后句为过去时，告诉秘密的动作又发生在其前因，此地应用过去完成时，但它
        在情态动词 ought to 后，所以用have。
14、比较need和dare
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　（需要, 要求） need + n. / to do sth
2）情态动词： need，只用原形need后加do，否定形式为need not。 
   Need you go yet?
   Yes, I must. / No, I needn't.
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 done

情态动词知识体系：

 

几组词的辨析：

1、need和dare的用法：
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
（1）用作情态动词：
 如：—Need I come? 我需要来吗？
         —Yes, you must. 需要。
         You needn′t telephone him now. 你现在不必打电话给他。 
         I don′t think you need worry. 我想你不必发愁。 
         She dare not go out alone at night. 她晚上不敢一个人出去。
         How dare you say I′m unfair? 你竟敢说我不公平？
         Not one of them dared mention this.他们谁也不敢提这件事。
（2）用作实义动词：
如：You don′t need to do it yourself. 你不必亲自做这件事。
        We need to tell them the news. 我们需要把这消息告诉他们。
        The table needs painting(to be painted.). 桌子需要油漆一下。
        We should dare to give our own opinion.我们要敢于提出自己的观点。
        He did not dare(to) look up. 他不敢抬头看。
        I dare day he′ll come again. 我想他会再来的。
2、can和be able to：
（1）情态动词can只有两种时态形式，现在式can和过去式could，而be able to有多种时态形式。
如：Mary can play the piano. She has been able to play it since she was 5. 玛丽会弹钢琴。她五岁起就会弹了。
（2）用在过去时中，could经常表示能够做某事，事实上不一定去做，而was∕were able to则表示“过去做成了某事”。在否定句中两者可通用。
如：He could swim across the English Channel. But he didn′t feel like it that day.
        他能游过英吉利海峡，但那天他不想游。
        Yesterday I was able to get home before the heavy rain. 昨天我在下大雨前赶到了家里。
3、must和have to：
must表示主观意志，而have to表示由于客观因素不得不做某事。must没有过去式，除在间接引语中可用于表示过去时间，在直接引语中表示过去时间应该用had to代替。
如：I told her that she must give up smoking. 我叫她必须戒烟。
        We had to get everything ready that night. 我们那晚得把一切准备就绪。
4、would和used to：
（1）usedto表示过去与现在或过去某时与后来的情况有不同，而would只表过去的情况。
如：People used to think that the earth was flat.  过去人们认为地球是平的。（现在人们不这么认为。） 
        She would go out for a walk in the morning when she was in the country.
        在乡下时，她总是在早晨去散会儿步。（可能现在仍有散步的习惯。）
（2）used to可表示过去的习惯动作和经常的情况，而would只表示过去的习惯动作。
如：He used to∕would smoke while writing. 过去他写东西时常抽烟。
        She used to be fat. 她过去很胖。

情态动词表推测的三种句式：

1、在肯定句中一般用must(一定)，may（可能），might/could（也许，或许）。
如：He must/may/might know the answer to this question? 他一定/可能/也许知道这个问题的答案。 
        It is cold in the room. They must have turned off the heating. 屋里很冷，他们肯定把暖气关了。
2、否定句中用can't/couldn't (不可能), may not/might not(可能不)。
如：It can't/couldn't be the headmaster. He has gone to America.  这不可能是校长，他去美国了
        He may not/might not know the scientist. 他也许不认识那位科学家。
3、疑问句中用can/could(能……?)。
如：Could he have finished the task? 他可能把任务完成了吗？
        Can he be at home now? 他现在能在家吗？
注：以上三种句式中情态动词的语气按程度都是依次递减的。Might, could并非may, can的过去式，而表示语气较为委婉或可能性较小。

情态动词表推测的三种时态：

1、对将来情况的推测，用“情态动词+动词原形”。
如：She must/may/might/could arrive before 5.  5:00前她一定/可能/也许到。
        She must/may/might/could walk miles and miles among the hills without meeting anyone.
        她一定/可能/也许会在山里一连走好几英里而遇不到一个人。
2、对现在或一般情况的推测，用“情态动词+be”，“情态动词+bedoing”或“情态动词+动词原形”。
如：He must/may/might/could be listening to the radio now. 他一定/可能/也许正在听收音机。
        He can't(couldn't)/may(might) not be at home at this time. 这个时候他不可能/可能不在家。
        Mr. Bush is on time for everything. How can(could) he be late for the opening ceremony?
        布什先生一向准时，这次开幕式他怎么可能迟到呢？
3、对过去情况的推测，用“情态动词+have+过去分词”。
如：It must/may/might/ could have rained last night. The ground is wet. 地湿了，昨晚肯定/可能/也许下雨了。
        The door was locked. He can(could) not/may(might) not have been at home. 门锁着，他不可能/可能不在家。       
        Can/Could he have gotten the book？难道他找到书了吗？
注：情态动词should/ought to表推测时，意为“想必会，理应……”但与“have+过去分词”连用时，则又可构成虚拟语气意为“本应该做某事却没做”。
如：It's seven o'clock. Jack should/ought to be here at any moment.
        现在七点钟了，杰克理应随时到达。（推测）    
        She should/ought to have attended your birthday party, but she had to look after her mother in hospital.（虚拟）
        她本该出席你的生日晚会的，可是她得在医院照顾她妈妈。 
        Tom should not/ought not to have told me your secret, but he meant no harm.（虚拟）
        汤姆本不该告诉我你的秘密，可是他并无恶意。

1、掌握情态动词的基本含义及基本用法。
2、掌握虚拟语气中情态动词的用法。

能力要求：综合运用
课时要求：2
考试频率：必考
分值比重：4