1、最全情态动词的用法情态动词的用法一can和could情态动词用法例子补充说明can/could表示能力1I can speak fluent English now, but I couldnt last year.Can表现在能力；Could表示过去能力.可用be able to代替；was/were able to 表示成功做了某事在肯定句中，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could，may，might。1.I may stay at home this weekend.（实际可能性）2.Peter mi
2、ght come to join us.(实际可能性) 3.It will be sunny in the daytime ,but it could rain tonight.(实际可能性)1.can用于否定和疑问句(could不限)2.can(be)表示有时候会（常与sometimes,attimes连用）表示请求和允许。表示请求，口语中常用could代替can，使语气更委婉。1Can we turn the air conditioner on?.2.I wonder if I could just ask you to sign this.1.请求用could 语气委婉 2.允许不用
3、could.表示对现在的动作或状态进行主观的猜测，主要用在否定句和疑问句中。1It cant be easy caring for a man and a child who are not your own.2Can the man over there be our head master?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?2This cant be true.3How can you be so crazy!特别提示：（1）could用来表示请求时，语气委婉，主要
4、用于疑问句，不能用于肯定句，回答应该用can（即：could不能用于现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区分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
5、youll be able to carry them on your 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 bui
6、lding.(3) 惯用形式“cannot too”表示“无论怎么也不（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情态动词用法例子补充说明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 com
7、e in and wait?2May I smoke here?No, you mustnt(或No, youd better not.)1.请求用might语气更委婉。 2.允许时用may，表示“可以”（表示允许时不用might）。在表示请求、允许时，might比may语气更委婉些。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，在日常用语中，用Can I征询对方意见更为常见。1Might I borrow your pen?2I wonder if I might speak to your son.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；
8、用might代替may时，则语气显得更加不肯定。1It may rain this afternoon.2I suppose he might have missed the train.常用于肯定句（might可能最小）may用于祈使句表示祝愿1May you succeed！惯用句式：“may well+ 动词原形”，意为“完全能，很可能”，相当于to be very likely to“may as 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 el
9、se.1There is nothing to do, so I may as well go to bed.2You may as well tell us now, well find out sooner or later.3I suppose we might as well go home.二must和have to情态动词用法例子补充说明Musthave to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
10、fast in the street.3We mustnt waste any more time.1.must多表主观、现在/将来义务; have to多表客观、过去义务 2. mustnt表禁止；否定用neednt / dont have to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)表示有把握的推测，意为“一定、准是” 1It must be my mother.2You must be hungry
11、after a walk.3There must be a hole in the wall. 只用肯定句。在否定句/疑问句中用can/could“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 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 h
12、ard when I was your age.2In order to take the exam, well have to finish the whole book by the 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.3四shall和should情态动词用法例句补充说明shall用于第一、二、三人称构成的疑问句，表示征求对方意见或请求指示1Shall I open the window?2Shall we s
13、ay 6 oclock, then?3What shall I get for dinner?表规章、法令、预言：“必须”用于所有人称 Every competitor shall wear a number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 shall 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 a
14、s I tell you, you shall not go to the party. (威胁) should表示劝告或建议，意为“应该”1What should I do?2Should I trust him?3You 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 be a nice day tomorrow.2Try phoning Robert, he should be home now.3He should be around sixty years old.肯定
15、的语气没有must用于推测时强 This pen ought to /should be yours.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)3If things should change suddenly, please let me kno
16、w. (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?五will和would情态动词用法例句补充说明will/would用于表示意志或意愿。will指现在，would指过去。1He is the man who will go his own way. (他是个自行其是的人。)2They said they would meet us at 10:30
17、at the station.Would此时为will过去式，无意义差别表示请求、建议等，用would比用will委婉、客气。1Will you please take a message for him?2Would you please tell me your telephone number?此意用于疑问句，常与you连用 Will you give me a piece of paper?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。)3When
18、we worked in the same office, we would often have coffee together.Would表过去反复的动作/某种倾向(相对于used to无“现已无此习惯”之义。)表示推测，意为“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.3It would be about ten oclock when he left home.此意表对目前事物的预料。That will be the postman r
19、inging.(would表示过去/现在；will表示现在/将来)表示功能，意为“能，行”。惯用形式：will do/would do表示“解决问题”、“就行”。1That will be all right.2Either pen will do.3It would not do to work too late.（工作太晚不行。）叙述真理：The tree will leave without water for 3 months.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 wo
20、uldnt listen to me.特别提示：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 morn
21、ing. Sometimes she 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 needn
22、t)2You neednt have 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 unders
23、tanding.(need+名词，need 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
24、中1Dare you tell her 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 i
25、t?七ought的用法：情态动词用法例句补充说明Shouldought 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 oughtnt to.（1）should 用于疑问句中表示说话人对某事不能理解，惋惜，感到意外，赞 叹，愤怒、惊异等感情，意为“竟会”，有时也用于陈述句中 （2）Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能， 相当于“万一”的意思。表示推测。注意与must表示推测是的区别1He must be home
26、by now. (断定他已到家)2He ought to be home by now. (不十分肯定)3This is where the oil must be. (比较直率)4This is where the oil ought to be. (比较含蓄)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
27、ought to get him to receive good education.八“情态动词+have done”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
28、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 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
29、 such a foolish thing?3The boy cant have finished reading the 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 d
30、one better, but you were too careless.might have done表示“本来可能，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 this 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 o
