初中英語(yǔ)復(fù)習(xí)要點(diǎn)：助動(dòng)詞與情態(tài)動(dòng)詞
（一）助動(dòng)詞
有be, have, do, will, shall，它們本身沒(méi)有詞義，只和實(shí)義動(dòng)詞的一定形式構(gòu)成復(fù)合謂語(yǔ)，用來(lái)表示時(shí)態(tài)和語(yǔ)態(tài)，構(gòu)成否定、疑問(wèn)及加強(qiáng)語(yǔ)氣等。
1、be (am, is, are, were, been)
(l)"be + -ing"構(gòu)成進(jìn)行時(shí)態(tài)；（2）"be + 過(guò)去分詞"構(gòu)成被動(dòng)語(yǔ)態(tài)；（3）"be + 動(dòng)詞不定式"構(gòu)成復(fù)合謂語(yǔ)：①表示按計(jì)劃安排要發(fā)生的事。The prime minister is to visit Japan next year. 總理將于明年訪問(wèn)日本。② 用于命令。You're to do your homework before you watch TV.你得做完了作業(yè)才能看電視。
2、have (has, had)
(1)"have+過(guò)去分詞"構(gòu)成完成時(shí)態(tài)。如：Have you seen the film ? (2)"have been + -ing"構(gòu)成完成進(jìn)行時(shí)態(tài)。如：What have you been doing these days? 這些日子你一直在干什么?
3、do (does, did)
(1)"do not + 動(dòng)詞原形"構(gòu)成行為動(dòng)詞的否定式。如：His brother doesn't like playing basket.；(2)"Do + 主語(yǔ) + 動(dòng)詞原形"構(gòu)成行為動(dòng)詞的一般疑問(wèn)句。Does he go to school by bike every day? (3)"do + 動(dòng)詞原形"用于祈使句或陳述句中表示加強(qiáng)語(yǔ)氣。如：I did go to see him, but he wasn't in我確實(shí)去看望他了，但他不在家。Do do some work. 請(qǐng)一定做點(diǎn)什么；(4)代替前面剛出現(xiàn)的動(dòng)詞以避免重復(fù)。My mother told me to go to bed early. So I did.
4.will, shall (would, should)
"will (shall+動(dòng)詞原形"構(gòu)成一般將來(lái)時(shí)，一般來(lái)說(shuō)shall用于第一人稱，will用于第二人稱或第三人稱，口語(yǔ)中常用will代替shll，如：We will have a meeting to discuss the problem.
（二）情態(tài)動(dòng)詞
情態(tài)動(dòng)詞表示說(shuō)話人對(duì)某一動(dòng)作或狀態(tài)的態(tài)度，可以表示"可能"、"可以"、"需要"、"必須"或"應(yīng)當(dāng)"等之意。情態(tài)動(dòng)詞沒(méi)有人稱和數(shù)的變化。但不能單獨(dú)作謂語(yǔ)動(dòng)詞用，必須和不帶to的不定式連用構(gòu)成謂語(yǔ)動(dòng)詞。只有情態(tài)動(dòng)詞ought要和帶to的動(dòng)詞不定式連用，在句中作謂語(yǔ)用。
將情態(tài)動(dòng)詞置于主語(yǔ)之前即構(gòu)成其疑問(wèn)式，在情態(tài)動(dòng)詞之后加not既構(gòu)成其否定式�，F(xiàn)將各情態(tài)動(dòng)詞的基本用法分述如下：
1、can和could (could為can的過(guò)去式) 的基本用法
(1)表示能力，如：He can speak English better than you. (2)在疑問(wèn)句和否定句中表示"懷疑"、"猜測(cè)"或"可能性"，如：Can this green bike be Liu Dong's? (3)表示"許可"時(shí)can可以和may換用，如：You can (may) go home now. (4)如果要表示語(yǔ)氣婉轉(zhuǎn)，可用could代替can，這時(shí)could不再是can的過(guò)去式，如：Could you come again tomorrow? (5)can和be able to都可表示能力，兩者在意思上沒(méi)有什么區(qū)別。但是can只能有現(xiàn)在式和過(guò)去式，而be able to則有更多的形式，如：He will be able to do the work better.
2、may和might (might為may的過(guò)去式)的基本用法
(1)表示允許或征詢對(duì)方許可，有"可以"之意，如：You may use my dictionary. 在回答對(duì)方說(shuō)"可以做某事"或"不可以做某事"時(shí)，一般多不用may或 may not，以避免語(yǔ)氣生硬或不容氣。而用比較婉轉(zhuǎn)的說(shuō)法進(jìn)行回答。如：---- May I use this dictionary? ---- Yes, please. 或 ---- Certainly. 在請(qǐng)求對(duì)方許可時(shí)，如果Might I…? 就比用May I…? 語(yǔ)氣更婉轉(zhuǎn)些，如：May I have a look at your new computer? 但是表示"阻止"或"禁止"對(duì)方做某事時(shí)，要用must not代替may not，如：---- May we swim in this lake? ---- No, you mustn't. It's too dangerous. (2)may或 might都可以表示可能性，表示"或許"、"可能"之意，如果用might表示可能性，則語(yǔ)氣更加不肯定，如：They may (might) be in the library now .
3、must的基本用法
(1)must表示"必須"、"應(yīng)該"之意，其否定式 must not，縮寫(xiě)形式為 mustn't，表示"不應(yīng)該"，"不準(zhǔn)"、"不許可"或"禁止"之意，如：We must study hard and make progress every day. You mustn't touch the fire. (2)對(duì)以must提出的疑問(wèn)句，如作否定回答時(shí)，要用needn't或用don't (doesn't) have to (不 必)來(lái)回答，而不用mustn't，因?yàn)閙ustn't表示的是"禁止"或"不許可"之意，如：---- Must we finish the work tomorrow? ---- No, you needn't (don't have to), but you must finish it in three days. (3)在肯定句中must可以表示推測(cè)，表示"一定"或"必定"之意，如：---- Whose new bike can it be? ---- It must be Liu Dong's. I know his father has just bought him a new one.
4、can, could, may, must后接完成式的用法
(1)can, could后接完成式的用法：①在否定句或疑問(wèn)句中表示對(duì)過(guò)去發(fā)生過(guò)的事情的"懷疑"或"不肯定"的態(tài)度，Could he have said so? ②在肯定句中，可以表示過(guò)去可能做到而實(shí)際并沒(méi)做到的事情，有"勸告"或"責(zé)備"的語(yǔ)氣，英語(yǔ)語(yǔ)法《語(yǔ)法復(fù)習(xí)十一：助動(dòng)詞與情態(tài)動(dòng)詞》。如：---- When did you answer her letter? ---- Only yesterday. ---- It's too late. You could have answered it earlier, I am sure. (2)may, might后接完成式的用法 ①表示對(duì)過(guò)去某事的推測(cè)，認(rèn)為某一件事情在過(guò)去可能發(fā)生了。如果使用might，語(yǔ)氣就比較婉轉(zhuǎn)或更加不肯定，如：Mary might have learned some Chinese before. ②可以表示過(guò)去本來(lái)可以做到而實(shí) 際沒(méi)有做到的事情，有"勸告"或"責(zé)備"的語(yǔ)氣，如：You didn't do the work well that day. You might have done it better. (3)must后接完成式的用法：表示對(duì)過(guò)去某事的推測(cè)，認(rèn)為某事在過(guò)去一定做到 了，如：Liu Dong isn't in the classroom. He must have gone to the library.
5、have to 的基本用法：
have to和must的意義相近，只是 must側(cè)重表示說(shuō)話人的主觀看法，而have to 則表示客觀需要，如：I must study hard. I had to give it up because of illness.
6、ought to的`基本用法
(l)表示根據(jù)某種義務(wù)或必要"應(yīng)當(dāng)"做某事，語(yǔ)氣比should強(qiáng)，例如：Everyone ought to obey the traffic regulations. (2)表示推測(cè)，注意與must表示推測(cè)時(shí)的區(qū)別：He must be home by now .(斷定他已到家)，He ought to be home by now .(不十分肯定)，This is where the oil must be.(比較直率) ，This is where the oil ought to be. (比較含蓄) ；(3)"ought + have+ 過(guò)去分詞"表示過(guò)去應(yīng)做某事而 實(shí)際未做。例如：You ought to have helped him. (but you didn't) 這時(shí)，ought與 should可以互相換用。注意，在美國(guó)英語(yǔ)中ought to 用于否定和疑問(wèn)句時(shí)to可以省略。例如：Ought you smoke so much? You oughtn't smoke so much.
7、dare的基本用法
(l)dare (dared為其過(guò)去式) 作情態(tài)動(dòng)詞用時(shí)，主要用于否定句，疑問(wèn)句和條件從句中，如：Dared he bread the traffic regulations again? (2)在現(xiàn)代英語(yǔ)中dare常用作行為動(dòng)詞，其變化與一般行為動(dòng)詞相同，如：She dares to stay at home alone at night.
8、need的基本用法
(1)need作情態(tài)動(dòng)詞用時(shí)，主要用于否定句和疑問(wèn)句中，如：He needn't worry about us now. (2)need也可作為行為動(dòng)詞用，可用于肯定句，否定句和疑問(wèn)句中，其后可接名詞、代詞、動(dòng)名詞或帶 to 的動(dòng)詞不定式為其賓語(yǔ)。如：You need to practise reading aloud every day. (3)needn't后接完成式可以表示過(guò)去做了一件本來(lái)不必要做的事情，如：---- Did you answer the letter yesterday? ---- Yes, I did. ---- But you needn't have answered it.
9、shall的基本用法
(1)shall用作情態(tài)動(dòng)詞時(shí)，用于第二、三人稱，表示說(shuō)活人的意愿，可表示"命令"、"警告"、"強(qiáng)制"、"威脅"或"允諾"等意，如：He shall go first, whether he wants to or not. (2)在疑問(wèn)句中，shall用于第一、三人稱，表示說(shuō)話人的征詢對(duì)方意見(jiàn)或請(qǐng)求指示，如：Shall I open the door?
10、should的基本用法
(1)should作為情態(tài)動(dòng)詞可以表示"建議"或"勸告"，有"應(yīng)該"之意，如：You should learn from each other. (2)should后接完成式表示過(guò)去沒(méi)有做到本來(lái)應(yīng)該做的事情，或是做了本來(lái)不應(yīng)該做的事情。如：You should have give him more help.
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