情态动词的用法归纳.doc

1、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。1 As a human being, anyone can make a mistake.2 I may stay at home this weekend.（实

2、际可能性）3 Peter might come to join us.(实际可能性) 表示请求和允许。1 Can 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。1 Can this be an excuse for not giving them help?2 How 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不能用于现在时态的简略答语中）

3、。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 own?但是，表

4、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（过分）”。如：

5、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。1 May I come in and wait?2 May I smoke here?No, you mustnt

6、(或No, youd better not.)表示请求、允许时，1 May 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；1 It may rain this afternoon.2 She may not be at home.may用于祈使句表示祝愿1 May you succeed.2 Long may he live! 愿他能持续住下去。3 May you have many more days as happy as this one.4 May 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.1 There 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1 You must come to school on time.2 You mustnt drive so fast i

8、n the 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.1 It must be my mother3.表示固执己见，“一定”。2 If 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。1 Th

9、e film is not interesting. I really must go now.2 I 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

10、 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。1 You mustnt go there.2 You 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1 Shall I open the window?2 Shall we say 6 oclock, then?3 What 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。1 Dont w

11、orry, you shall get the answer this afternoon.(允诺)2 He shall be sorry for it one day, I tell you. （警告）3 You shall do as I say. (命令)4 If 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”1 You 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

12、概，或许”1 It should be a nice day tomorrow.2 Try phoning Robert, he should be home now.3 He 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1 Ask 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)2 Should I be free tomorrow, Ill

13、come. (万一我明天有时间，我就过来)3 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。1 Why should anyone want to marry Tony?2 Dont ask me. How should I know?ought to do表示“应该”之意1 You ought to take care of him.2 Ought I go now?Yes, yo

14、u ought to. /No, you oughtnt to.表示推测。注意与must表示推测是的区别1 He must be home by now. (断定他已到家)2 He 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

15、get him to receive good education.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1 He 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，1 Will you please take a message for him?2 Would 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。1 Fish will die without water.2 Peopl