用心爱心专心1 情 态 动 词 小 结（一）情态动词概说1情态动词也是“辅助性”动词，用来表示说话人的语气或情态。情态动词所表示的情态有：请求、命令、允诺、可能、需要、敢于、愿望、义务、能力等。2情态动词本身有词义，但词义不完全，不能单独用作谓语，没有人称和数的变化，且后面只跟动词原形。如：她会唱英文歌曲。She cans sing an English song.（ ）She can sings an English song.（ ）She can sing an English song.（ ）3有些情态动词的过去时与其原形相同，有些与原形不同。(1) 与原形相同的有：must - must ought to - ought to (2) 与原形不同的有：can - could will - would may - might shall - should need - needed dare - dared have to - had to 4大多数的情态动词后面可以用动词不定式（多不带to）的进行时、完成时或被动形式，如： may, can, must 等。（二）情态动词的种类：（见下表）原形过去式词义cancould能maymight可以（或许）mustmust(had to)必须（不得不）willwould愿意shallshould应该needneeded需要daredared敢于（三）情态动词的否定形式：cannot - can t could not - couldn t may not- mayn t might not- mightn t must not - mustn t will not - won t would not - wouldn t need not - needn t shall not - shan t should not - shouldn t ought not - oughtn t dare not - daren t （四）常用情态动词的用法：1can 与 could 1） can 用心爱心专心2 （1）表示体力或脑力方面的“能力”，也能表示根据客观条件能做某事的“能力”。He can drive. Can you jump as far as he did? I can t catch up with Jim. can与 be able to 二者都表示“能够” ，区别是： can 只有现在时和过去式，而be able to可用于各种时态。如：I ll be able to speak French in half a year. He hasn t been able to finish it on time. （2）表示允许：You can go now. Can I use your bike? （3）表示推测：Who can it be? It can t be true.can 表示猜测或怀疑只用于疑问句及否定句中。2） could （1）can 的过去式，表示过去有能力及过去的可能性。He couldn t climb up the mountain. The news could be true. （2）表示客气地请求或委婉地陈述意见。Could you go skating with me tomorrow? I m afraid I couldn t give you an answer tonight.（3）表示惊异、怀疑、不相信等态度How could he say that? He couldn t be in Beijing. 2may 与 might 1） may （1）表示请求、许可、可以May I use your dictionary? Yes, please/certainly. May I come in? （2）表示推测说话人的猜测，认为某一事情“或许”或“可能”发生。It may rain this afternoon. I may leave for Hangzhou next week. （3）may 用于感叹句中可以表示祝愿或愿望。May you do well! May you have a good time! 2) might （1）用作 may 的过去式。We didn t know that he might be our new teacher. The accident might happen the day before yesterday. （2）替代 may 来表示现在时间的动作，主要于推测（但其可能性比may 更低） 。用心爱心专心3 I m afraid it might snow tomorrow. You might meet him at the conference. The movie might have finished now. （3）委婉地表示请求（不是过去式）。Might I ask you a question? Might you go there with me? 3must （1） 表示义务，命令或必要。Soldiers must obey orders. We must be strict with ourselves. （2） 表示肯定的推测：一定He must be at home.（对现在的猜测）I think you must have made a mistake. （对过去的猜测）He must be our new teacher. He can t be our new teacher. （3）此外还要弄清楚must 与 have to 的区别4will 与 would 1） will （1）表示意愿、决心。此时可用于各种人称。He wont come to see you.他不愿来见你。 （表示意愿）I will try my best to catch up with her.我将尽最大努力赶上她。（表示决心）（2）表示请求，此时仅限于“will you (please) , ？”句型中，仅用于第二人称和疑问句中。Will you please buy me an English-Chinese dictionary when you go to the bookstore? Will you have some rice? 2） would （1）will 的过去式，表示过去的意愿和决心。He said he would do everything for her, but she said she would never see him again. They believed that we would help them. （2）用于现在时， 表示委婉地提出请求，建议或看法。 此时 would 的用法比 will 更加委婉。Would you please show me the way to the museum? I would like to say something about it. will 和 would 用于“劝某人接受, ”时，只能用some，不能用any。如：Would you like some fish? 吃点鱼好吗？5shall 与 should 1） shall 征求对方意见或请求，用于第一、三人称。表示“要不要, ？”、 “ , 好吗？”Shall I open the window? Shall the doctor come? 用心爱心专心4 2） should （1）should 意思是“应该” ，表示劝告或建议（=ought to ）You should wash your hands before dinner. We should help each other. （2）用来表示可能性或猜测。He should be in the office now. I should be right. （3）should 有时能表示说话人的情感等。Its funny that they should be confident. （表示轻视）Why should I do that for you? （表示不满）（4）should 后接动词不定式（不加to）时，若用于肯定句，表示某件事本应该完成却未完成；若用于否定句，则表示某事不该发生却发生了。You should have told us the truth. （应该告诉却没有）He should have known the importance of it. 应该知道却不知道）We shouldnt have left so early.（不应该早出来，可已经做了）6need 1）need意思是“需要，必须” ，主要用于否定句和关系问句中。You needn t come so early. Need I take part in the Party? 2) need 引导的疑问句，肯定回答时多用must，否定回答时用neednt。Need he come? Yes, he must. No, he needn t.3) need 后接名词做宾语时，表示“需要”某件事物，此时用作实义动词，与一般的实义动词用法完全一样。如：We need three apples. He doesn t need so many books. 7. ought ought 只有一种形式，后面常与to 连用，意思是“应该” 。You ought to visit us often. Sorry, I ought to leave now. 在表示“应该”时，ought to 的语气比should 要强，比must 稍弱。8. dare 1) dare 意思是“敢”，用于肯定结构中时，后接加to 的动词不定式。The boy dared to climb up the tree. She should dare to question her teacher. 2）dare用于否定句或疑问句中时，与大多数的情态动词一样，后接不带to 的动词不定式。Dont dare do that again! 用心爱心专心5 The poor girl dare not go home. 9had better You had better see a doctor. You had better not leave now. Had I better wait for her? 练习检测1. Nobody _ do it. Let me _ . A. can, try B. can t, to try C. can, to try D. can t, trying2. “ _ you like _ bananas to eat?” “ Yes,please.”A. Would, some B. Will, any C. Could, any D. Can, some 3. “ Can you answer this question in English?” “ Sorry, I _.”A. needn t B. may not C. can t D. mustnt4. “ _ I borrow your dictionary?” “ Certainly, here you are.”A. Must B. May C. Need D. Shall 5.