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1、助动词,动词表示动作形态，但英语里有些动词并不表示动作形态，而是协助主动词表示时态（tenses）或语态（voices）。这些动词叫助动词（auxiliary verbs）,英语中助动词主要有两类：一是基本助动词，如have, do, be；二是半助动词, 如 be about to等三是情态助动词，如may, must, need等。,基本助动词,助动词可表示动词时态和语态,构成疑问句和否定句,例如 “have, has, had”用来构成完成时态； “be, is, are, am, been, was, were, being” 构成被动语态What do you do every da
2、y? Betty has completed her work on time .Jason is writing a new book. A rat was caught by a cat.,构成疑问句附加语，如： Mr. Chen has not become a businessman, has he? Jasons lectures are clear and easy-to-understand, arent they?,构成简短答语，如： -Will you help us with the gardening? Yes, I will. /No, I wont. -I have
3、seen that film before. -So have I. -William isnt a teacher. -Neither is his wife.,构成省略句，如： The boss doesnt often come to the factory and when he does, it is generally on Sunday.,半助动词,在功能上介乎主动词和助动词之间的一类结构，称为半助动词。常见的半助动词有be about to, be due to, be going to, be likely to, be meant to, be obliged to, be
4、 supposed to, be willing to, have to, seem to, be unable to, be unwilling to等。它们可与主动词搭配构成复杂动词词组并表示情态意义，有时也可与助动词搭配 ,例如:,He is unwilling to help me with my English. Every clause is obliged to obtain a finite verb. We were about to start when it rained. He seems to be very disappointed. I dont have to
5、buy a new house.,情态动词,情态动词有can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would) .,在肯定句中它们后边都要接 动词原形. 在否定句中，can, may, must 和dare后边加not；have to和ought to分别在have和ought后加not；had better和would rather的否定式分别是had better not和would rather not。这些情态动词与现在完成时连用在某种意义上有一定的虚拟性。,情态
6、动词+动词原形情态动词+动词完成式 情态动词+动词进行式 情态动词+动词完成进行式 某些情态动词的特殊用法,一、情态动词+动词原形,can表示体力或脑力方面的“能力”、“技能”或根据客观条件能做某种动作的“可能性”My grandma is over seventy, but she can still read without glasses.但表示人体力或智力的具体动作时须用 be able toHe was able to do that without any help.,may表示“允许，可以”，相当于be allowed to You may go now.May I use yo
7、ur computer? may或might可和as well连用，表示“建议”，译为“还是的为好”You may as well keep a certain distance from that mad man. You might as well go home now.,must表示“必须”或“应当”、“一定”在回答must引起的问题时，如果是否定的答复，不能用mustnt，而要用neednt或dont have to，因为mustnt是“一定不要”、“一定不能”的意思。 You must come to the classroom before eight. “Must we do
8、it now?” “No, you neednt.”,have to 加动词原形，表示“不得不”，“必须”，它比must更强调客观have to可用于多种时态，而must一般用于现在时，其过去时与将来时分别由had to与shall / will have to代替Tom had to work into the deep night everyday to earn a living.,should 表示“劝告”，“建议”或“义务”时，译作“应当”，或表示“预测”和“可能”He should take care of his parents as they are old enough no
9、t to live on themselves. He should be there now. should have done在虚拟语气中表示“责备或后悔,ought ，只有一种形式，即ought后必须加to，然后跟接动词原形表示“有义务”或“必要”做某事，译为“应当，应该” You ought not to make fun of him. He is not the one you laugh at but learn from.,dare作为情态动词时，主要用于疑问句和否定句，表示“敢”，后面跟不带to的动词不定式。如：How dare she do things like that
10、 to me? -Dare you catch the mouse?,Dare也用作实义动词，其后的动词不定式可带to也可不带to，且dare有人称和数以及时态的变化。例如： I dare to jump down from the top of the wall. She doesnt dare (to) meet her teachers eyes,need意为“需要”，既可作情态动词，也可作实义动词.作情态动词无人称或数的变化， 后接动词原形，如：You neednt worry.The president wondered whether he need send more soldi
11、ers,need 作为行为动词有人称和数的变化， 后面可接名词、代词、动名词及带to 的动词不定式；可用于肯定句、疑问句和否定句中，如：She needs help. I dont need to see the doctor. Do you need to go at once?,will (would)决心,愿望。 would 为 will 的过去式, 可用于各种人称。 Ill do my best to catch up with them. Its hot. Will you open the windows Would you like some coffee?,二. 情态动词+动词
12、完成式,must have v-ed 表示推测过去某事“一定”发生了。其否定形式为：cant / couldnt have v-ed, 表示过去不可能发生某事。例如： Since the ditch is full of water, it must have rained last night. You couldnt have met my grandmother. She died before you were born.,may (might)+have+ED分词：用于肯定句和否定句，表示对已发生事情的不肯定的推测，相当于“可能，大概，”其中might较may 语气更弱，把握更小 S
13、he might have gone to see her doctor last week, but I am not sure,should(ought to)+have+ED分词：肯定句表示过去本应发生的事却没有发生；否定句表示已发生了本不该发生的事。前者可译为“本应，”后者为“本不该” You should have apologized to her for not soon replying to the letterYou ought not to make fun of him. He is not the one you laugh at but learn from.,Ca
14、n /could have done 表示假设，与过去的事实相反。推测过去某动作“很可能”发生了. can和could一般用于否定句和疑问句，could的语气较can弱。 例如：He could have been very rich, but he cared for no money at all He cant have finished the work so soon.,neednt+have+ED分词：表示对过去不必做的事情却做了，可译为“其实不必” You neednt have waken me up; I dont have to go to work today.,表示推测
15、过去某动作发生的可能性时，就表示的可能性程度而言，must最大，could其次，may更次之，might最小。例如： “I wonder how Tom knew about your past.” “He must / could / may / might have heard of it from Mary.”,例题: I was really anxious about you. You _home without a word A. mustnt have B. shouldnt have left C. couldnt have left D. neednt have,三. 情态动
16、词+动词进行式,情态动词+行为动词进行式（即情态动词+ be + v-ing形式），表示推测或评论某动作现在是否正在进行。例如： He must be playing basketball in the room. She may be staying at home.,四.情态动词+动词完成进行式,情态动词+行为动词完成进行式（即情态动词+ have been + v-ing 形式），表示推测或评论过去某动作是否正在进行或一直在进行。例如： They should have been meeting to discuss the problem. He may / might have be
17、en buying stamps in the post office when you saw him.,五.用作情态动词的其他短语,would rather, would sooner, would (just) as soon, had rather, had better, had sooner, can not but, may (just) as well 等可用作情态动词 The soldier would sooner die than surrender. The brave soldier would as soon die as yield to such an enemy. If you dont like to swim, you may just as well stay at home.,这些短语后一般直接跟动词原形.would (had) rather, would (had) sooner, would (just) as soon后可跟that 引导的从句，that 常省去，从句要用虚拟语气。对现在和将来的假设用过去时，对过去的假设用过去完成时。例如： I would rather you came on Sunday. I would sooner you hadnt asked me to speak yesterday.,
