1、情态动词的用法归纳情态动词的用法归纳情态动词的用法要点一can和could情态动词用法例句can/could表示能力1“I dont think Mike can type.” “Yes, he can.”2I can speak fluent English now , but I couldnt last year.在肯定句中，表示客观可能性，并不涉及具体某事会发生，常用来说明人或事物的特征。要表达具体某事实际发生的可能性时，不用can，需用may，might。1As a human being, anyone can make a mistake.2I may stay at home
2、this weekend.（实际可能性）3Peter might come to join us.(实际可能性) 表示请求和允许。1Can we turn the air conditioner on?否定句中表推测“不可能”1He cant be at home.表示惊异、怀疑、不相信等态度，主要用在否定句、疑问句和感叹句中。1Can this be an excuse for not giving them help?2How can you be so crazy.特别说明：（1）could用来表示请求时，语气委婉，主要用于疑问句，不能用于肯定句，答语应用can（即：could不能用于现
3、在时态的简略答语中）。如：Could I use your dictionary?Yes, you can.(否定回答可用：No, Im afraid not.)(2)can和be able to辨析can(could)和be able to都可以表示能力，意思上没有区别。但can只有现在式和过去式，而be able to则有更多的形式。如：Ive always wanted to able to speak fluent English.Those bags look really heavy, are you sure youll be able to carry them on your
4、 own?但是，表示在过去某时的某一场合经过一番努力，终于做成了某事，通常不用could，而用was/were able to来表示。这时，was/were able to相当于managed to do或succeed in doing。如：After the accident it was a long time before she was able to walk again.The fire was very big, but most people were able to escape from the building.(3) 惯用形式“cannot too”表示“无论怎么也不
5、（过分）”。如： You cannot be too careful.你越小心越好。 惯用形式“cannot but+ 不定式（不带to）”表示“不得不，只好”。如： I cannot but admire her determination.我不得不钦佩你的决心。 二may和 might情态动词用法例句may/might表示允许、许可。否定回答一般用must not/mustnt,表示“禁止、阻止”之意，但也可以用had better not (最好别)或may not（不可以），语气较为委婉。1May I come in and wait?2May I smoke here?No, you
6、 mustnt(或No, youd better not.)表示请求、允许时，1May I borrow your pen?表示可能性的推测，通常用在肯定句和否定句中，含有“或许”“大概”“可能”之意；1It may rain this afternoon.2She may not be at home.may用于祈使句表示祝愿1May you succeed.2Long may he live! 愿他能持续住下去。3May you have many more days as happy as this one.4May she rest in peace.愿她安息。惯用句式：“may as
7、 well或might(just)as well+动词原形”意为“最好，满可以，倒不如”，相当于“had better或there is no reason to do anything else.1There is nothing to do, so I may as well go to bed.二must和have to情态动词用法例句must1.表示“必须，应该”之意，语气比should，ought to强烈。其否定形式mustnt表示“不准，不应该，禁止”等意1You must come to school on time.2You mustnt drive so fast in t
8、he street.在回答带有must的问句时，否定回答常用neednt或dont have to，表示“不必”，而不用mustnt1Must I come back before ten? Yes，you must.(No, you neednt)2.表示有把握的推测，意为“一定、准是、相必”，只用于肯定句中.1It must be my mother3.表示固执己见，“一定”。2If you must,I will tell you .have tohave to“必须，不得不”，意义与must相近。但must表示的是说话人的主观看法，而have to则往往强调客观需要。1The film
9、 is not interesting. I really must go now.2I have to go now, because my mother is in hospital.must只有一种形式，即现在式与过去式都是一种形式，而have to则涉及各种人称、时态等方面的变化形式。1I had to work hard when I was your age.2I will have to learn how to use a computer.3In order to take the exam, well have to finish the whole book by the
10、 end of this month .两者的否定意义不同，mustnt表示“禁止，不许”，dont have to表示不必。1You mustnt go there.2You dont have to go there.四shall和should情态动词用法例句shall用于第一人称构成的疑问句，表示征求对方意见或请求指示1Shall I open the window?2Shall we say 6 oclock, then?3What shall I get for dinner?用于第二、三人称陈述句中，表示说话人给对方的命令、警告、允诺或威胁。1Dont worry, you sha
11、ll get the answer this afternoon.(允诺)2He shall be sorry for it one day, I tell you. （警告）3You shall do as I say. (命令)4If you children dont do as I tell you, you shall not go to the party. (威胁) should表示劝告或建议，意为“应该”1You should read his new book.表示推测，用在肯定句中，对现在的情况或可能发生的事的主观推测或期待。意为“想必，大概，或许”1It should b
12、e a nice day tomorrow.2Try phoning Robert, he should be home now.3He should be around sixty years old.还可以用在if引导的条件句中，表示一件事听起来可能性很小，但也不是完全不可能，相当于“万一”的意思。从句谓语用should+动词原形构成，主句都一定用虚拟语气1Ask Tom to ring me up if you should see him. (你万一见到汤姆，请让他给我打个电话)2Should I be free tomorrow, Ill come. (万一我明天有时间，我就过来)3
13、If things should change suddenly, please let me know. (万一情况突变，请通知我)用于疑问句或感叹句中，表示意外、惊异的情绪，意为“竟会”，与why，what，how，who连用，如果是疑问句，则不需要回答。1Why should anyone want to marry Tony?2Dont ask me. How should I know?ought to do表示“应该”之意1You ought to take care of him.2Ought I go now?Yes, you ought to. /No, you oughtn
14、t to.表示推测。注意与must表示推测是的区别1He must be home by now. (断定他已到家)2He ought to be home by now. (不十分肯定)说明：should与ought to 表示“应该”时的区别should 表示自己的主观看法，而ought to的语气中，含有“按道理应该”之意。若要反映客观情况或涉及法律义务和规定，一般用ought to。如： You should help them with their work. You are his father. You ought to get him to receive good educa
15、tion.五will和would情态动词用法例句will/would用于表示意志或意愿。will指现在1He is the man who will go his own way. (他是个自行其是的人。)表示请求、建议等，1Will you please take a message for him?2Would you please tell me your telephone number?表示习惯或倾向，意为“总是，惯于”。will至现在，would指过去。1Fish will die without water.2People will talk. (人们总会说闲话。)表示推测，意为
16、“很可能，大概”。will表示推测比should把握大，比must把握小。1These things will happen.2That will be the messenger ringing.表示功能，意为“能，行”。惯用形式：will do/would do表示“解决问题”、“就行”。1Either pen will do.用于否定句中，意为“不肯”、“不乐意”1I wont listen to your nonsense.2No matter what I said, he wouldnt listen to me.表示说话时临时的决定。1. I will open the door
17、.特别说明：would与used to辨析would可用来表示过去反复出现的动作，但不能表示过去存在的状态，所以我们不能说：“she would be a quiet girl.”另外，would强调过去某种特定情况下的活动，是完全过去的事情，同现在没有联系。而used to则着眼于过去和现在的对比，隐含现在已不存在，动作或状态都可表示。Would可以表示不规则的习惯，used to则不可。如： He used to be a naughty boy and cause trouble. I used to get up at six in the morning. Sometimes she
18、 would take a walk in the neighboring woods. In those days, whenever I had difficulties, I would go to Mr. Chen for help.六need和dare情态动词用法例句need用于表示“需要，必要”之意。做情态动词时，仅用于否定句和疑问句，只有现在时，过去式要用neednt have，疑问式用need+人称?,否定式用need not(即neednt），1Need we leave soon? Yes, you must.(No, you neednt)2You neednt have
19、 hurried.(=It was not necessary for you to hurry，but you did).你当时不必这么匆忙。做实义动词时，其变化与一般的实义动词相同，后接带to的不定式（need doing = need to be done ）,过去式用needed、did you need?和didnt need,肯定式用needs/needed/need,疑问式用do、does、did提问，否定式要在前面加dont、doesnt、didnt1. A job like nursing needs patience and understanding.(need+名词，n
20、eed understanding=need to be understood,需要被理解)2He needs to see a doctor.(need to do)3Do you still need volunteers to help clean up after the party?(need somebody to do something) 4They didnt need to start so early.(do not need to do)dare用于表示“敢于”之意。做情态动词，没有人称和数的变化，主要用于否定句、疑问句和条件状语从句中1Dare you tell he
21、r the truth? Yes, I dare. /No, I darent.3How dare you accuse me of lying!4He darent admit this.用作实义动词时，其变化与一般的实义动词相同。在肯定句中，dare后接带to的不定式；否定句中，dare后既可接带to的不定式，也可接不带to的不定式。1Only a few journalists dared to cover the story.2He doesnt dare (to) go there alone.3Dont you dare (to) touch it?七“情态动词+have done
22、”用法情态动词+have done用法例句must have done 表示主观上对过去已经发生的行为进行推测，意为“想必，准是，一定做了某事”1She must have gone through a lot.2He must have visited the White House during his stay in the United States.may/might have done表示对过去已发生行为的推测，意为“也许/或许已经（没有）“。一般用于肯定句或否定句中，不用于疑问句。用might则表示语气更加不肯定。1You may have learnt the news.2He
23、 may not have heard his name called.3Sorry Im late. I might have turned off the alarm clock and gone back to sleep again.canhave donecannot have done表示对过去发生的行为的怀疑和不肯定，通常用在否定句和疑问句中。（can换成could时语气委婉）1Where can she have gone?2Could he have done such a foolish thing?3The boy cant have finished reading t
24、he book so soon because it is difficult even to an adult.could have done可用于肯定句中，表示“可能已经”之意，此外，还可以表示过去能做而没做的事，有一种对过去为付诸实施的事情的惋惜。1He could have killed himself driving at a dangerous speed.2You could have been more considerate.3You could have done better, but you were too careless.might have done表示“本来可
25、能，但实际上没有发生的事情”。另外，还可以表示“本来应该或可以做某事”之意，含有轻微的责备语气。1You should not swim in that sea. You might have been eaten by a shark.2He might have given him more help, thought he was busy.should/ought to have done用于肯定句时，表示本该做某事，而实际上未做；用于否定句时，则表示不该做的事反而做了。1He should have known that the police would never allow th
26、is sort of thing.2You shouldnt have done it so carelessly.3You ought to have returned the book earlier.4You ought not to have refused his offer.neednt have done表示做了本来不必去做的事。注意：didnt need to do表示“没必要做而实际上也没有做某事”1You neednt have watered the plants, for it is going to rain.2I didnt need to buy the dictionary. I had a copy at home.1
