情態(tài)動詞的語法特征

1、情態(tài)動詞的語法特征1）情態(tài)動詞不能表示正在發(fā)生或已經(jīng)發(fā)生的事情，只表示期待或估計某事的發(fā)生。2）情態(tài)動詞除 ought 和 have 外，后面只能接不帶to 的不定式。3） 情態(tài)動詞沒有人稱，數(shù)的變化，即情態(tài)動詞第三人稱單數(shù)不加-s。4） 情態(tài)動詞沒有非謂語形式，即沒有不定式，分詞，等形式。比較 can 和 be able to1)cancould 表示能力；可能(過去時用 could),只用于現(xiàn)在式和過去式(could) 。 be able to 可以用于各種時態(tài)。They will be able to tell you the news soon.他很快就能告訴你消息了。2)只用 be

2、able toa. 位于助動詞后。b. 情態(tài)動詞后。c. 表示過去某時刻動作時。d. 用于句首表示條件。e. 表示成功地做了某事時，只能用 was/were able to， 不能用 could。 He was able to flee Europe before the war broke out.= He managed to flee Europe before the war broke out.注意： could 不表示時態(tài)1) 提出委婉的請求，（注意在回答中不可用 could）。- Could I have the television on?- Yes, you can. / N

3、o, you can't.2) 在否定，疑問句中表示推測或懷疑。He couldn't be a bad man.他不大可能是壞人比較 may 和 might1） 表示允許或請求；表示沒有把握的推測；may 放在句首，表示祝愿。May God bless you!He might be at home.注意：might表示推測時，不表示時態(tài)。只是可能性比may小。2） 成語：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.典型例題Peter _come

4、 with us tonight, but he isn't very sure yet.A. mustB. mayC. canD. will答案 B. 表可能性只能用may.此句意可從后半句推出。比較 have to 和 must1)兩詞都是 '必須 '的意思， have to 表示客觀的需要，must表示說話人主觀上的看法，既主觀上的必要。My brother was very ill, so I had to call the doctor in the middle of the night.我弟弟病得很厲害，我只得半夜里把醫(yī)生請來。(客觀上需要做這件事)He

5、said that they must work hard. 他說他們必須努力工作。 （主觀上要做這件事）2) have to 有人稱、數(shù)、時態(tài)的變化，而 must 只有一種形式。但 must 可用于間接引語中表示過去的必要或義務(wù)。He had to look after his sister yesterday.3） 在否定結(jié)構(gòu)中：don't have to表示 "不必 "mustn't表示 "禁止 "，You don't have to tell him about it.你不一定要把此事告訴他。You mustn't

6、 tell him about it.你一定不要把這件事告訴他。must 表示推測1) must 用在肯定句中表示較有把握的推測，意為"一定 "。2) must 表對現(xiàn)在的狀態(tài)或現(xiàn)在正發(fā)生的事情的推測時，must 后面通常接系動詞be的原形或行為動詞的進(jìn)行式。You have worked hard all day.You must be tired.你辛苦干一整天， 一定累了。（對現(xiàn)在情況的推測判斷）He must be working in his office.他一定在辦公室工作呢。比較：He must be staying there.他現(xiàn)在肯定呆在那里。He mu

7、st stay there.他必須呆在那。3) must 表示對已發(fā)生的事情的推測時，must 要接完成式。I didn't hear the phone. I must have been asleep.我剛才沒有聽到電話，我想必是睡著了。4) must 表示對過去某時正發(fā)生的事情的推測，must 后面要接不定式的完成進(jìn)行式。-Why didn't you answer my phone call?-Well, I must have been sleeping, so I didn't hear it.5) 否定推測用 can't。If Tom didn&#

8、39;t leave here until five o'clock, he can't be home yet.如果湯姆五點(diǎn)才離開這兒，他此時一定還未到家。表示推測的用法can, could, may, might, must 皆可表示推測，其用法如下：1）情態(tài)動詞 + 動詞原形。表示對現(xiàn)在或?qū)淼那闆r的推測，此時動詞通常為系動詞。I don't know where she is, she may be in Wuhan.2）情態(tài)動詞 + 動詞現(xiàn)在進(jìn)行時。表示對現(xiàn)在或?qū)碚谶M(jìn)行的情況進(jìn)行推測。At this moment, our teacher must be

9、correcting our exam papers.這時，我們老師想必在批改試卷。3）情態(tài)動詞 + 動詞完成時。表示對過去情況的推測。We would have finished this work by the end of next December.明年十二月底前我們很可能已完成這項(xiàng)工作了。The road is wet. It must have rained last night.地是濕的，昨天晚上一定下雨了。4）情態(tài)動詞 + 動詞的現(xiàn)在完成進(jìn)行時。表示對過去正在發(fā)生事情的推測。Your mother must have been looking for you.你媽媽一定一直在找

10、你。5）推測的否定形式，疑問形式用can't, couldn't 表示。Mike can't have found his car, for he came to work by bus this morning.邁克一定還沒有找回他的車，因?yàn)樵缟纤亲财噥砩习嗟?。注意?could, might 表示推測時不表示時態(tài)，其推測的程度不如can, may。情態(tài)動詞 + have +過去分詞1) may(might) have + done sth, can (could) have + done sth 表示過去， 推測過去時間里可能發(fā)生的事情。Philip may

11、 (might) have been hurt seriously in the car accident.Philip can (could) have been hurt seriously in the car accident.2)must have +done sth，對過去時間里可能發(fā)生的事情的推測，"諒必 " 的意思。-Linda has gone to work, but her bicycle is still here.-She must have gone by bus.語氣較強(qiáng)，具有 "肯定 "，3) ought to have

12、done sth, should have done sth本應(yīng)該做某事，而事實(shí)上并沒有做。否定句表示 "不該做某事而做了 " 。 You ought to (should) have been more careful in this experiment.ought to 在語氣上比should 要強(qiáng)。4) needn't have done sth 本沒必要做某事 I dressed very warmly for the trip, but Ineedn't have done so. The weather was hot.5) would lik

13、e to have done sth本打算做某事I would like to have read the article, but I was very busy then.shouldshould和 和ought to ought to都為 "應(yīng)該 " 的意思，可用于各種人稱。-Ought he to go?-Yes. I think he ought to.表示要求，命令時，語氣由should（應(yīng)該）、 had better 最好）、 must（必須）漸強(qiáng)。had better 表示 " 最好 "had better 相當(dāng)于一個助動詞，它只有一種形

14、式，它后面要跟動詞原形。had better do sthhad better not do sthIt is pretty cold. You'd better put on my coat.She'd better not play with the dog.had better have done sth表示與事實(shí)相反的結(jié)果，意為"本來最好"。You had better have come earlier.would rather表示 "寧愿"would rather do would rather not do would ra

15、ther than寧愿而不愿。還有 would sooner, had rather, had sooner都表示 "寧愿 "、 " 寧可 " 的意思。If I have a choice, I had sooner not continue my studies at this school.I would rather stay here than go home. = I would stay here rather than go home.典型例題-Shall we go skating or stay at home?-Which _ do?

16、A. do you ratherB. would you ratherC. will you rather答案 B。本題考查情態(tài)動詞rather 的用法， would rather +do問句， would提前，所以選B。will 和 wouldD. should you rathersth 意為 " 寧愿 "，本題為疑注意：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 ? 表示肯定含義的請求勸說時， 疑問

17、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, won't you 是一種委婉語氣。Won't you sit down?情態(tài)動詞的回答方式問句 肯定回答否定回答Need you ?Must you ?Yes, I must.No,I needn't/don't have to.典型例題1）-Could I borrow your dictionary?-Yes, of course, you_.A. mightB. willC. canD. should答案 C.co

18、uld 表示委婉的語氣，并不為時態(tài)。答語中of course，表示肯定的語氣，允許某人做某事時，用can 和 may 來表達(dá)，不能用could 或 might。復(fù)習(xí)：will與 you連用，用來提出要求或下命令。should 與 you 連用，用來提出勸告。2）-Shall I tell John about it?-No, you _. I've told him already.A. needn'tB. wouldn'tC. mustn'tD. shouldn't答案 A 。needn't 不必，不用。 wouldn't 將不 , 不

19、會的。 mustn't 禁止、不能。 shouldn't不應(yīng)該。本題為不需要，不必的意思，應(yīng)用needn't。3）-Don't forget to come to my birthday party tomorrow.-_.A. I don'tB.I won'tC. I can'tD. I haven't答案 B.will既可當(dāng)作情態(tài)動詞，表請求、建議、也可作為實(shí)義動詞表" 意愿、意志、決心 "，本題表示決心，選B。帶 to 的情態(tài)動詞帶 to 的情態(tài)動詞有四個： ought to, have to, used to, be to, 如加上 have got to ,(=must), beable to，為六個。它們的疑問，否定形式應(yīng)予以注意：Do they have to pay their bill before the end of the month?She didn't use to play tennis before she was fourteen.You ought not