1、Grammar: Modal verbs,How many modal verbs do you know?,can could may might shall should must will would ought to,have to dare (darent) need (neednt) used to,表示推測(cè),不表示推測(cè),modal verbs,1. 情態(tài)動(dòng)詞有一定的意義，只表示期待或估計(jì)某事的發(fā)生，不能表示正在發(fā)生或已經(jīng)發(fā)生的事情。 2. 沒(méi)有人稱(chēng)和數(shù)的變化，即情態(tài)動(dòng)詞第三人稱(chēng)單數(shù)不加-s。 3. 不能獨(dú)立使用，它和后面的動(dòng)詞構(gòu)成謂語(yǔ)。 4. 情態(tài)動(dòng)詞除ought和have外，后

2、面只能接動(dòng)詞原形 5. 情態(tài)動(dòng)詞沒(méi)有非謂語(yǔ)形式，即沒(méi)有不定式，分詞等形式。,只作情態(tài)動(dòng)詞的 can/could, may/might, ought to, must,可情態(tài)可實(shí)義的 need, dare,可情態(tài)可助動(dòng)詞的shall/should, will/would,相當(dāng)于情態(tài)動(dòng)詞的have to,情態(tài)動(dòng)詞的語(yǔ)法特征,位置: 情態(tài)動(dòng)詞在句中放在謂語(yǔ)動(dòng)詞之前, 謂語(yǔ)動(dòng)詞前若有助動(dòng)詞,則在助動(dòng)詞之前,疑問(wèn)句中, 情態(tài)動(dòng)詞則在主語(yǔ)之前。,I can see you. Come here. 我能看見(jiàn)你，過(guò)來(lái)吧。 He must have been away. 他一定走了。 What can I do

3、 for you? 我能幫你嗎？ How dare you treat us like that！ 你怎能那樣對(duì)待我們！,1. 表示能力或客觀可能性，還可以表示請(qǐng)求和允許。如： Can you finish this work tonight? Man cannot live without air. Can I go now? Yes, you can.,can和could的用法,注意：could也可表示請(qǐng)求，語(yǔ)氣委婉，主要用于疑問(wèn)句，不可用于肯定句，答語(yǔ)應(yīng)用can（即could不能用于現(xiàn)在時(shí)態(tài)的簡(jiǎn)略答語(yǔ)中）。如： Could I come to see you tomorrow? Yes,

4、 you can. （否定答語(yǔ)可用No, Im afraid not.） can表示能力時(shí)，還可用be able to代替。如： Ill not be able to come this afternoon.,2. 表示驚異、懷疑、不相信的態(tài)度。（主要用在否定句、疑問(wèn)句或驚嘆句中）,Can this be true? How can you be so careless! This cannot be done by him.,3. “can(could) + have + 過(guò)去分詞”的疑問(wèn)或否定形式表示對(duì)過(guò)去發(fā)生的行為懷疑或不肯定。如：,He cannot have been to that

5、 town. Can he have got the book?,4. cannottooenough表示無(wú)論怎樣也不過(guò)分,越越好,eg. I cannot thank you too much for all your help to me. You cannot be too carefull when you traveling alone.,may和might的用法,1. 表示許可。 表示請(qǐng)求、允許時(shí)，might比may的語(yǔ)氣更委婉一些，否定回答時(shí)(口語(yǔ)中常用) no , you cant . or , yes, please 用mustnt表示“不可以”、“禁止”、“阻止”之意(具有

6、強(qiáng)烈禁止的意思)如：,You may drive the car. Might I use your pen? No, you mustnt. 用May I . 征詢(xún)對(duì)方許可在文體上比較正式，在口氣上比較客氣。在日?？谡Z(yǔ)中，用Can I . 征詢(xún)對(duì)方意見(jiàn)在現(xiàn)代口語(yǔ)中更為常見(jiàn)。,2. 用于祈使句中表示祝愿。如： May you succeed! May you have a nice day!,3. 表示推測(cè)、可能（疑問(wèn)句不能用于此意）。 He may be very busy now. 4. “may(might) + have + 過(guò)去分詞”表示對(duì)過(guò)去發(fā)生的行為的推測(cè)。如： He may n

7、ot have finished the work.,will和would的用法,1. 表示請(qǐng)求、建議等，would比will委婉客氣。如： Would you pass me the book? 2. 表示意志、愿望和決心。如： I will never do that again. They asked if we would do that again.,3. 用“will be”和“will(would) + have + 過(guò)去分詞”的結(jié)構(gòu)表示推測(cè)，主要用于第二、三人稱(chēng)。前者表示對(duì)目前情況的推測(cè)，后者表示對(duì)已經(jīng)完成的動(dòng)作或事態(tài)的推測(cè)。如：,This will be the book y

8、ou want. He will have arrived by now. The guests would have arrived by that time. I thought you would have finished this by now.,It would be about ten when he left home. What would she be doing there? I thought he would have told you all about it.,4. Would可表示過(guò)去反復(fù)發(fā)生的動(dòng)作或某種傾向。Would表過(guò)去習(xí)慣時(shí)比used to正式，并沒(méi)有“

9、現(xiàn)已無(wú)此習(xí)慣”的含義。如：,The wound would not heal. During the vacation he would visit me every week.,5. 表料想或猜想。如,Would更多的用來(lái)表示語(yǔ)氣而不是時(shí)態(tài) Will/would you please do., Would you like to do., Would you mind doing. 都表示建議、詢(xún)問(wèn)、請(qǐng)求等。 e.g., Would/ Will you mind opening the windows? I would / will do anything for you , sir. 有時(shí)

10、甚至只能用would而不用will e.g., I would like. Would you like.? They would love. He would rather ,2. “must be + 表語(yǔ)”的結(jié)構(gòu)表示推測(cè)，它的否定或疑問(wèn)式用can代替must。 This must be your pen.,3. “must + have + 過(guò)去分詞”的結(jié)構(gòu)常用在肯定句中，表示對(duì)過(guò)去發(fā)生的行為的推測(cè)。它的否定或疑問(wèn)式用can代替must。 He must have been to Shanghai.,shall和should的用法,一.Shall的用法：,1. Shall用于第一、第三人

11、稱(chēng)疑問(wèn)句中，表示說(shuō)話人征求對(duì)方的意見(jiàn)或向?qū)Ψ秸?qǐng)示。如：,Shall we begin our lesson? When shall he be able to leave the hospital? What shall we do this evening?,2. Shall用于第二、第三人稱(chēng)，表示說(shuō)話人給對(duì)方命令、警告、允諾或威脅。如：,You shall fail if you dont work harder. He shall have the book when I finish reading. He shall be punished.,（警告）,（允諾）,（威脅）,二.Sho

12、uld的用法：,1. Should表示勸告、建議、命令，其同義詞是ought to；在疑問(wèn)句中，通常用should代替ought to。如：,You should go to class right away. Should I open the window?,Should的含義較多，用法較活，現(xiàn)介紹三種其特殊用法。請(qǐng)看下面的句子： I should think it would be better to try it again. 我倒是認(rèn)為最好再試一試。 You are mistaken, I should say. 依我看，你是搞錯(cuò)了。 I should advise you not

13、to do that. 我倒是勸你別這樣做。 This is something I should have liked to ask you. 這是我本來(lái)想問(wèn)你的。,從以上例句可以看出：情態(tài)動(dòng)詞should用于第一人稱(chēng)時(shí)可以表示說(shuō)話人的一種謙遜、客氣、委婉的語(yǔ)氣。,Should還可以用在if引導(dǎo)的條件從句，表示一件事聽(tīng)起來(lái)可能性很小，但也不是完全沒(méi)有可能。相當(dāng)于“萬(wàn)一”的意思。從句謂語(yǔ)由should加動(dòng)詞原形構(gòu)成，主句謂語(yǔ)卻不一定用虛擬語(yǔ)氣。如：, Ask her to ring me up if you should see her. If you should change your mind, please let us know. Should I (If I should) be free tomorrow I will come.,你萬(wàn)一見(jiàn)到她，請(qǐng)讓她給我打個(gè)電話。,萬(wàn)一你改變主意，請(qǐng)通知我們。,萬(wàn)一我明天有時(shí)間，我就來(lái)。,此外，Why(or How) + should結(jié)構(gòu)表示說(shuō)話人對(duì)某事不能理解，感到意外、驚異等意思。意為“竟會(huì)”。如：, Why should you be so late today? 你幾天怎么來(lái)得這么晚？ Where is Betty living? 貝蒂住在哪里？ How should I