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來自：要學(xué)習(xí)網(wǎng)
 閱讀原文情態(tài)動詞表示說話人的語氣和情態(tài)。如需要、可能、愿意、懷疑等。情態(tài)動詞有一定的詞義，但不完整，必須和主要動詞的原型一起構(gòu)成謂語。常用的情態(tài)動詞有：can, could, may, might, must, have to, ought to, need, dare, shall, will, should, would, be able to,及半情態(tài)動詞be to do, had better等。 情態(tài)動詞的基本用法： （一）can“能夠” 1.表示體力或腦力方面的能力，或根據(jù)客觀規(guī)律能做某事的能力。 (1)can表“能夠”時，既可指現(xiàn)在也可指將來。 (2)can與be able to的區(qū)別： ① 表“能力”時二者同義 No one can / is able to do it. ② be able to常側(cè)重經(jīng)過努力有能力做到，有多種時態(tài)。can側(cè)重自身的能力，只有一般現(xiàn)在時和一般過去時。 ③ was / were able to do表示通過努力克服困難或在一定的條件下成功地做了某事，側(cè)重結(jié)果，相當(dāng)于managed to do或succeeded in doing...。could僅表自身的能力或本領(lǐng)，但未必成功做到。 With the help of the firemen, they were able to leave the burning house. He was able to swim across the river. In the end, we were able to rescue the workers trapped in the fire. 2.表示“許可，允許”。在疑問句中表示請求，許可；否定句中表示“不許”。此時常與may通用： May/Can I do it? This sort of thing can't go on! 這類事情不能再繼續(xù)了！ 注意 can not有時可以表示“禁止”相當(dāng)于mustn't： You can't（mustn't，are not allowed to）play football in the street.你不可以在大街上踢球。 3.表示推測，強(qiáng)調(diào)客觀可能性：“可能、會”。主要用于疑問句和否定句。表示推測、估計時，后邊可根據(jù)不同情況用動詞原形、進(jìn)行式、完成式。 She can't be waiting for you. He can't have gone there alone. 4.表驚訝、疑慮。 How can it be that he was late for the opening ceremony? （二）could 1．表“能力”“可能性”“許可”，為can的過去式。 He said he could go. 2. could用于一般現(xiàn)在時中表委婉、客氣地提出問題或陳述看法。（此時不是can的過去式，要用can回答以顯得爽快。此時can和could沒有時間的差別，只是could語氣更客氣些。） -Could I borrow your pen? - Yes, you can. （三）may, might (may的過去式為might） 1.表示許可，有“可以”的意思，詢問或說明一件事可不可以做，有時可以用can互換。 You may go now. 否定式may not表示“不可以、禁止、阻止”等，常用must not（＝mustn't）代替。may用于疑問句中時，回答多避免用may，以免顯得太嚴(yán)肅或不客氣。 2.表推測：“或許、可能”。表示一件事或許會發(fā)生，只用在陳述句中。 It may rain tomorrow. 3. may可以表祝愿，一般放在句首構(gòu)成倒裝句式： May you succeed! =I hope you may succeed.祝您成功! May that day come soon! 希望這一天早日來到！ 4. might是may的過去式，表可以做的事或可能發(fā)生的事。 She suggested a few books which I might buy. 5. might用于一般現(xiàn)在時比may委婉，或表示現(xiàn)實的可能性更小一些。 He might come soon. 6. may (just) as well, might as well.“不妨…”（可以用來提出建議）。它們比had better顯得謙遜或不那么有把握，所以had better通常是不用于長者或上司的。同時，had better有時帶有威脅口吻。（may well為“完全能；滿可以；很可能”，表示有可能或有充分理由做某事。well是may的程度副詞） I needn't wait; I may as well tell you now. 我不必等，我不妨現(xiàn)在就告訴你。 Since it's a fine day, we might as well walk. 既然是好天氣，我們一不妨走走。 It may well be that the question is still under discussion. 那很可能是該問題仍在討論中。 （四）must 1.表示必須要做的事，意為“必須”，否定式mustn't表示不準(zhǔn)、不許、禁止等。在回答帶有must的問句時，不用mustn't，而用needn't或don't have to。 I must go now. Must I go home? No，you needn't. / Yes, you must. must在表“必須”時與have to相近，have to強(qiáng)調(diào)客觀需要，must著重主觀看法。另外must不像have to能有更多的時態(tài)。 2.表推測，暗含很大的可能性，意為“一定、肯定”，只用于“肯定句”中。此時其否定式為can't,“絕非”。 He must be over sixty. There must be a mistake. 3.偏偏、硬要、干嘛（指做令人不快的事） Must you shout so loudly? 你干嘛這么大聲喊？ （五）shall 1.表示命令、履行義務(wù)、意愿、許諾、警告、強(qiáng)制、威脅、決心等，一般用于二、三人稱中，并用于陳述句。 You shall have my answer tomorrow. （允諾） You shall be sorry for it one day, I tell you. （警告） You shall do as I tell you. （命令或吩咐） We shall go, whatever may happen. （決心） 2.征求聽話人意見和指示，用在一、三人稱的疑問句中。 Shall he come to see you? ＝Do you want him to see you? （六）should should是shall的過去式，但它同時又是一個有單獨意義的情態(tài)動詞。 1.表達(dá)職責(zé)、義務(wù)，作“應(yīng)當(dāng)”講，常與ought to互換。但ought to側(cè)重反映客觀情況，should側(cè)重表示主觀看法。 2.表示預(yù)測可能性，并譯作“可能，（按道理）應(yīng)該”。 They should come here now. 3.用于委婉、謙遜地提出意見或建議。 I should think you are right.我以為你是對的。 4. should用于某些從句中表虛擬語氣： ①用于表示建議、命令的動詞的賓語從句中。表示建議、命令的動詞有suggest（表“建議”時）, advise（忠告）, recommend（推薦）, order（命令）, demand(要求）urge（力勸）,require(要求）, request(請求）,desire（渴望）, ask / insist（表“堅決要求”含義時）等詞的賓語從句的謂語應(yīng)由“should+動詞原形”構(gòu)成，此時should可省略。 He suggested that I（should）do the Job. ②用于①項中動詞的名詞形式以及wish, instruction, order, plan, idea等的表語從句或同位語從句中。 It is my wish that you（should）do so. ③用于某些主語從句中。 It is demanded we（should）get everything ready by the end of the week. ④should表驚奇、懷疑、不滿、意外等，常用于“Why/How should...”句型和expect, think, imagine, believe等詞的賓語從句中作“竟，竟然”解。 It's a pity that he (should) be so careless. 真可惜他竟然如此粗心。 ⑤在if, lest, for hear that, in case引起的從句中，謂語用should +動詞原形, 把可能性減弱。（譯作“萬一”，“要是真的”）。 If you should decide to accept, please phone me. =Should you decide to accept,please phone me. 萬一你決定接受，請打電話給我。 ⑥should (ought to)+ have done表“過去該做某事，卻沒做”，含有“責(zé)備、內(nèi)疚”意。 She should (ought to) have helped you a lot. ⑦shouldn't (ought not to) + have done. 表做了不該做的事情，含有責(zé)備、后悔意。 （七）ought to 1. ought to表示“應(yīng)該”，語氣比should 強(qiáng)。 We ought to help each other in our work. 2. ought to表示因責(zé)任、義務(wù)等該做的事，具客觀性。 should多表示某件事宜于做，帶有一定的主觀意見。 You're my father. You ought to look after me. 3. ought to表根據(jù)事實非常可能的事，意為“理應(yīng)...”。 He is her neighbor, so he ought to know her address. 4. ought (not) to have done =should (not) have done。 （八）will ①表示意愿、意志和決心，用于各種人稱。 I'll do my best. ②表示各種傾向或習(xí)慣動作。 Fish will die out of water. -Who can close the door? -I will（I'll do it）我來吧！ 本句難點是：不能用I'm going to do it .或I'm to do it.而只能用will，因為本句話表反射性動作，不表計劃、打算。 ③表示一種揣想，用于二、三人稱。 They will have arrived by now.他們大概已經(jīng)到了。 ④用于疑問句中，表邀請、請求。 Will you give me a piece of paper? ⑤will 在表示經(jīng)常性、習(xí)慣性的含義時，有時可理解為“難免；總是”。 These things will happen.這種事難免要發(fā)生。 Boys will be boys.男孩畢竟是男孩。 Accidents will happen.事故難免會發(fā)生。 ⑥表猜測時，表“想必…”，would的可能性要比will小。 （九）would would是will的過去式，would + v.構(gòu)成過去將來時。除此之外，它還是單獨的情態(tài)動詞。 ①表示過去時間的“意志”、“愿望”和“決心”。 I told him that I would go along with him. ②委婉提出請求、建議或看法, 比will委婉?？隙ù鹫Z用will。 Would you help him? Yes, I will. ③表示過去的習(xí)慣動作和過去某種傾向。 When he was a child he would（used to）play football. would與used to的區(qū)別 ① used to主要用于今昔習(xí)慣的對比，表明過去如何而現(xiàn)在已不再如此。而would只表示過去習(xí)慣，不暗示現(xiàn)在。 ②used to用于表過去的習(xí)慣動作或過去一貫存在的情況、狀態(tài)，would則表過去習(xí)慣或傾向性的動作，不能表情況或狀態(tài)。故used to接動作動詞（work，stay等）也可接非動作動詞（like, have等），would只接動作動詞。 There used to be a house here. ④would用于固定習(xí)語中 would like sth. would like to do sth. would rather +動詞原形（than + v原形） I would rather do it myself. I would like to help you. He'd rather die than let me think he was a failure. 他寧愿死也不愿讓我認(rèn)為他是個失敗者。 ●would rather…than… （十）need 需要, need既可做實義動作，又可作情態(tài)動詞。 1. need作情態(tài)動詞主要用于疑問句、否定句，否定式為needn't. 沒有過去式形式，表達(dá)過去意義時仍用need。 Need you go soon? We needn't hurry. Need I come? No, you needn't (don't have to）/Yes, you must. 注意 need問句的肯定回答用must，否定回答用needn't或don't have to. 2.用在有否定意思的句子中。（帶有no, hardly等否定詞的句子）。 I hardly need say how much I missed you. 3. need作實義動詞有人稱、數(shù)、時態(tài)的變化?？隙ㄊ剑?/font>need to do。否定式：don't need to do。 注意 need doing = need to be done Does he need to know it? The windows need cleaning. 4. needn't have done表示“本不必做…（卻做了）”。 I needn't have bought the book. You needn't have told them about it. （十一）dare “敢”，既是實義動詞，又是情態(tài)動詞，用法如下： 1. dare作情態(tài)動詞主要用于疑問、否定及條件句中，后接動詞原形。沒有人稱和數(shù)的變化，但有時態(tài)變化，過去式為dared。 Dare you go home alone? He dare not tell the truth. 2. dare作實義動詞時，后跟不定式，用于肯定、否定、疑問等各種結(jié)構(gòu)。有人稱、數(shù)、時態(tài)變化，過去式為dared。 3.用于固定習(xí)語: “I dare say”意思是“我敢說，我認(rèn)為”。 I dare say you are my friend. 情態(tài)動詞表推測的用法歸納 1.“情態(tài)動詞+動詞原形”表示對通常或現(xiàn)在的行為或情況的推測。 He must know you.他一定了解你。 She may live here.她可能住在這里。 2.“情態(tài)動詞 + be doing”用于對可能正在發(fā)生的動作的推測，“應(yīng)當(dāng)正在…，可能正在...” He can't be reading. They must be waiting for you. ①此結(jié)構(gòu)間或可表示“即將，將要”這類意思。 I must be leaving now. 3.“情態(tài)動詞 + have done”結(jié)構(gòu)表示對已經(jīng)發(fā)生的事情的推測、責(zé)怪、后悔、遺憾等。 ① must have done，表示對過去事情把握極大的推測，意為“必定已經(jīng)”； “may（might) have done”為把握不大的猜測“可能已經(jīng)”。 注意must表示推測時，通常只用肯定句中。 否定句為can't（couldn't）have done 疑問句can (could)... have done... ? I didn't hear the telephone, so I must have been asleep. He can't have studied English before. ② may (might) have done還可表責(zé)備，“本來可以…”。 could have done表示“本能夠做某事而沒做”，指能力因素或可能性，可表示站在現(xiàn)在角度看過去（較委婉）也可指站在過去角度看過去的過去。 He might have given you more help, even though he was very busy. 他本應(yīng)可以給你更多幫助，盡管他非常忙。 He could have walked to the station, it was so near. 我們本可以走著去火車站，這么近。 ③should (ought to) have done 表示“本該做某事，但實際上沒做” should not（ought not to) have done 表示“本不該做某事卻做了” The plant is dead. I should have given it more water. （本該多澆水，而實際沒有） Tom ought not to have told me your secret. 湯姆本不該把你的秘密告訴我（但他告訴了）。 ④needn't have done.本不必做…（但實際卻做了）（didn't need to do表示本不必做而實際上也沒有做）。 I needn't have watered the flowers, for it's going to rain. ⑤will/would have done可表示推測，也可表示與過去事實相反。 They will have arrived by now. 他們大概已經(jīng)到了。 The car would have been out of control if he had not reacted quickly. 要不是他反應(yīng)快，車子就會失控。 |
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