1、情態(tài)動(dòng)詞教學(xué)講義一、 情態(tài)動(dòng)詞的用法1. must（1） must表示自己的主觀看法或要求別人必須做某事，意為“必須，應(yīng)該”。We must learn English hard. 我們必須努力學(xué)習(xí)英語(yǔ)。（2） must表示推測(cè)，意為“準(zhǔn)是，一定”，一般指可能性很大。The woman must be Li Leis mother. 那個(gè)婦女一定是李雷的母親。（3） must表示推測(cè)時(shí)，其否定式不用mustnt, 而用cant.The door is closed. He cant be at home.（4） mustnt表示“不可以，禁止”。You mustnt play on the r

2、oad. 你不可以在路上玩。（5） 以must開(kāi)頭的疑問(wèn)句，肯定回答用must，否定回答用neednt，意為“不必”。（6） must與have to的區(qū)別：must表示主觀的看法，have to表示客觀的需要。must只有一種形式，而have to有多種形式，第三人稱單數(shù)現(xiàn)在時(shí)用has to，過(guò)去式用had to，將來(lái)時(shí)態(tài)用will have to。2. needneed既可用作情態(tài)動(dòng)詞，又可用作實(shí)義動(dòng)詞。用作情態(tài)動(dòng)詞時(shí)，它只有一種形式，后跟不帶to的動(dòng)詞不定式，只用于否定句和疑問(wèn)句。用作實(shí)義動(dòng)詞時(shí)，它有動(dòng)詞的全部形式，即現(xiàn)在時(shí)單數(shù)第三人稱needs，現(xiàn)在分詞needing，過(guò)去式和過(guò)去分詞

3、needed，后跟帶to的不定式，可用于一切句式。3. 比較can和be able to（1） can, could表示“能力，可能”，（過(guò)去時(shí)用could），只用于現(xiàn)在式和過(guò)去式。be able to可以用于各種時(shí)態(tài)。They will be able to tell you the news soon.（2） 以下情況下只用be able to:A. 位于助動(dòng)詞后B. 情態(tài)動(dòng)詞之后C. 表示過(guò)去某時(shí)刻動(dòng)作時(shí)D. 用于句首表示條件E. 表示成功地做了某事時(shí)，只能用was/were able to，不能用could。He was able to flee Europe before the w

4、ar broke out.= He managed to flee Europe before the war broke out.戰(zhàn)爭(zhēng)爆發(fā)前他得以逃離歐洲。【注意】could不表示時(shí)態(tài)，其特殊用法有：（1） 提出委婉的請(qǐng)求，（注意在回答中部可用could）-Could you lend me your bike?-Yes, you can. / No, you cant.（2）在否定、疑問(wèn)句中表示推測(cè)或懷疑He couldnt be a bad man.4. 比較may與might（1） 表示允許或請(qǐng)求；表示沒(méi)有把握的推測(cè)；may放在句首，表示祝愿。May you succeed!He mi

5、ght be at home.【注】might表示推測(cè)時(shí)，用might代替may時(shí)，有時(shí)語(yǔ)氣更委婉，更不肯定，這時(shí)might不表示時(shí)態(tài)。（2） 成語(yǔ)搭配：may/might as well, 后面接不帶to的不定式，意為“不妨”。If that is the case, we may as well try.5. 比較have to和must（1） 兩詞都是“必須”的意思，have to表示客觀的需要，must表示說(shuō)話人主觀上的看法，即客觀上的必要。My mother was ill, so I had to look after her at home. （客觀上需要做這件事）He said

6、 that they must work hard. （主觀上要做這件事）（2） have to有人稱、數(shù)、時(shí)態(tài)的變化，而must只有一種形式，但must可用于間接引語(yǔ)中表示過(guò)去的必要或義務(wù)。He had to look after his sister yesterday.（3） 在否定結(jié)構(gòu)中，dont have to表示“不必”，mustnt表示“禁止”You dont have to tell him about it.You mustnt tell him about it.6. 表示推測(cè)的用法Can, could, may, might, must都可表示推測(cè)，其用法如下：（1） 情

7、態(tài)動(dòng)詞+動(dòng)詞原形表示對(duì)現(xiàn)在或?qū)?lái)的情況的推測(cè)，此時(shí)動(dòng)詞通常為系動(dòng)詞。I dont know where she is, she may be in Shenzhen.（2）情態(tài)動(dòng)詞+動(dòng)詞現(xiàn)在進(jìn)行時(shí)表示對(duì)現(xiàn)在或?qū)?lái)正在進(jìn)行的情況進(jìn)行推測(cè)。At this moment, our teacher must be correcting our exam papers.（3）情態(tài)動(dòng)詞+動(dòng)詞完成時(shí)表示對(duì)過(guò)去情況的推測(cè)We would have finished this work by the end of next December.The road is wet. It must have raine

8、d last night.（4） 情態(tài)動(dòng)詞+動(dòng)詞的現(xiàn)在完成進(jìn)行時(shí)表示對(duì)過(guò)去正在發(fā)生事情的推測(cè)。Your mother must have been looking for you.（5） 推測(cè)的否定形式，疑問(wèn)形式用cant, couldnt表示Mike cant have found his car, for he came to work by bus this morning.【注意】could, might表示推測(cè)時(shí)不表示時(shí)態(tài)，其推測(cè)的程度不如can, may.7. should和ought to二者都為“應(yīng)該”的意思，可用于各種人稱。-Ought he to go?-Yes. I th

9、ink he ought to.表示要求、命令時(shí)，語(yǔ)氣由should應(yīng)該，had better最好，must必須 漸強(qiáng)。8. had betterhad better表示“最好”，相當(dāng)于一個(gè)助動(dòng)詞，它只有一種形式，它后面要跟動(dòng)詞原形。It is pretty cold. Youd better put on my coat.Youd better not play with the dirty dog.9. would rather would rather表示“寧愿”，would ratherthan寧愿而不愿I would rather stay here than go home.= I

10、 would stay here rather than go home.10. will和would（1） would like; Would like to do = want to “想要”，為固定搭配。Would you like to go with me?（2） Will you? Would you like? 表示肯定含義的請(qǐng)求勸說(shuō)時(shí)，疑問(wèn)句中一般用some，而不是any。Would you like some cake?（3） 否定結(jié)構(gòu)中用will, 一般不用would, wont you是一種委婉語(yǔ)氣。Wont you sit down？11. 情態(tài)動(dòng)詞的回答方式Need

11、you? Yes, I must. / No, I neednt.Must you? I dont have to.12. 帶to的情態(tài)動(dòng)詞帶to的情態(tài)動(dòng)詞有四個(gè)：ought to, have to, used to, be to, 它們的疑問(wèn)，否定形式應(yīng)予以注意。Do they have to pay their bill before the end of the month?She didnt use to play tennis before she was fourteen.You ought not to have told her all about it.Ought he to

12、 see a doctor at once?Ought to本身作為情態(tài)動(dòng)詞使用，其他的詞作為實(shí)義動(dòng)詞使用，變疑問(wèn)，否定時(shí)，須有do等助動(dòng)詞協(xié)助。13. 比較need和dare這兩詞既可做實(shí)義動(dòng)詞用，又可做情態(tài)動(dòng)詞用。作為情態(tài)動(dòng)詞，兩者只能用于疑問(wèn)句，否定句和條件句。Need做實(shí)義動(dòng)詞時(shí)后面的不定式必須帶to，而dare做實(shí)義動(dòng)詞時(shí)，后面的to常可以省略。（1） 實(shí)義動(dòng)詞; need 需要，要求need+n./ to do sth.（2） 情態(tài)動(dòng)詞：need，只用原形need后加do, 否定形式為need not.Need you go yet？ 你還需要走嗎？Yes, I must. / N

13、o, I neednt.（3） need的被動(dòng)含義：need，want, require, worth(adj.)后面接doing也可以表示被動(dòng)。Need doing = need to be done二、 例題講解1.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【析】would rather+do sth 意為“寧愿”，本題為疑問(wèn)句，would提前，故選B.2.Shall I tell John

14、 about it ？- No, you _. Ive told him already.A.neednt B.wouldnt C.mustnt D.shouldnt【析】neednt表不必，不用，依題意，選A.3.Dont forget to come to my birthday party tomorrow. - _.A. I dont. B. I wont C. I cant D. I havent【析】will可作情態(tài)動(dòng)詞，也可作實(shí)義動(dòng)詞表“意愿，意志，決心”，本題表示決心，故選B.4. It _ be Helen. She has gone to Beijing.A.cant B.

15、mustnt C.may D.should【析】cant表示不可能，肯定不是，依題意選A.三、 隨堂練習(xí)1. Must I hand in the homework now?No, you _.A.mustnt B.cant C.neednt D.may not 2. You _ talk so loud in the library.A.neednt B.mustnt C.cant D.not3. You must be here at six tomorrow morning. - Sorry. I _ be here so early.A.need B.may C.must D.cant4.Dont be late. You _ be there on time.A.must B.can C.may D.neednt5.- _ I use your dictionary? -Certainly,