【英语语法】13个情态动词使用技巧.doc

情态动词的语法特征:1）情态动词不能表示正在发生或已经发生的事情,只表示期待或估计某事 的发生；2 ）情态动词除ought和have外,后面只能接不带to的不定式；3 ）情态动词没有人称,数的变化■即情态动词第三人称单数不加・s ;4 ）情态动词没有非谓语形式,即没有不定式,分词,等形式—、比较 can 和 be able to1 ） can could表示能力；可能（过去时用could）,只用于现在式和过去式（could）be able to可以用于各种时态They will be able to tell you the news soon.他很快就能告诉你消息了2 ）只用 be able toa. 位于助动词后b. 情态动词后c. 表示过去某时刻动作时d・用于句首表示条件e.表示成功地做了某事时,只能用was/were able to ,不能用couldoHe was able to flee Europe before the war broke out. =He managed to flee Europe before the war broke out.注意:could不表示时态）提出委婉的请求,（注意在答中不可用could 1 Could I have the television on? Yes, you can. / No, you cant・2 ）在否定f疑问句中表示推测或怀疑。

He couldnt be a bad man.他不大可能是坏人二比较may和might1 ）表示允许或请求；表示没有把握的推测；may放在句首,表示祝 May God bless you!He might be at home・注意:might表示推测时r不表示时态只是可能性比may小2 ）成语:may/might as well f后面接不带to的不定式.意为”不妨” If that is the case, we may as well try.典型例题Peter come with us tonight, but he isnft very sure yet.A. must B. may C. can D. will答案B.表可能性只能用may.此句意可从后半句推出三.比较have to和must1）两词都是■必须的意思,have to表示客观的需要f must表示说话人主 观上的看法,既主观上的必要My brother was very ill, so I had to call the doctor in the middle of the night.我弟弟病得很厉害,我只得半夜里把医生请来。

客观上需要做这件事）He said that they must work hard.他说他们必须努力工作主观上要做这 件事）2） have to有人称、数、时态的变化,而must只有一种形式但must可 用于间接引语中表示过去的必要或义务He had to look after his sister yesterday.3） 在否定结构中：don*t have to 表示”不必”mustnt表示”禁止” fYou dont have to tell him about it.你不一定要把此事告诉他You mustn*t tell him about it.你一定把这件事告诉他1) must用在肯定句中表示较有把握的推测,意为”一定”2) must表对现在的状态或现在正发生的事情的推测时，must后面通常接系 动词be的原形或行为动词的进行式You have worked hard all day.You must be tired.你辛苦干一整天,—定 累了对现在情况的推测判断)He must be working in his office.他一定在办公室工作呢比较：He must be staying there・他现在肯定呆在那里。

He must stay there・他必须呆在那3) must表示对已发生的事情的推测时,must要接完成式I didnt hear the phone. I must have been asleep.我刚才没有听到, 我想必是睡着了4) must表示对过去某时正发生的事情的推测,must后面要接不定式的主成进行式Why didnt you answer my phone call? Well, I must have been sleeping, so I didnt hear it.5）否定推测用cantIf Tom didnt leave here until five oclock, he cant be home yet.如果汤 姆五点才离开这儿，他此时一定还未到家1. 表示推测的用法can, could, may, might, must皆可表示推测,其用法如下：1 ）情态动词+动词原形表示对现在或将来的情况的推测,此时动词通常为系动词1 dont know where she is, she may be in Wuhan・2 ）情态动词+动词现在进行时表示对现在或将来正在进行的情况进行推测。

At this moment, our teacher must be correcting our exam papers・这时,我们老师想必在批改试卷3 ）情态动词+动词完成时表示对过去情况的推测We would have finished this work by the end of next December.明年十二月底前我们很可能已完成这项工作了The road is wet. It must have rained last night.地是湿的,昨天晚上一定下雨了4 )情态动词+动词的现在完成进行时表示对过去正在发生事情的推测Your mother must have been looking for you.你妈妈一定一直在找你5 )推测的否定形式■疑问形式用carTt, couldrft表示Mike cant have found his car, for he came to work by bus this morning. 迈克一定还没有找回他的车,因为早上他是坐公共汽车来上班的注意:could, might表示推测时不表示时态,其推测的程度不如can, mayo六、情态动词+ have +过去分词1) may(might) have + done sth, can (could) have + done sth 表示过去 f 推测过去时间里可能发生的事情。

Philip may (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 ■对过去时间里可能发生的事情的推测■语气较强■具有”肯定”,”谅必啲意思 Linda has gone to work, but her bicycle is still here・ She must have gone by bus・3) ought to have done sth, should have done sth本应该做某事■而事实上并没有做否定句表示“不该做某事而做了”You ought to (should) have been more careful in this experiment.He ought not to have thrown the old clothes away.(事实上已扔了)ought to在语气上比should要强4) needrft have done sth 本没必要做某事I dressed very warmly for the trip, but I neednt have done so. The weather was hot.5) would like to have done sth 本打算做某事I would like to have read the article, but I was very busy then・%1. should 和 ought toshould和ought to都为”应该”的意思f可用于各种人称。

Ought he to go? Yes・ I think he ought to.表示要求,命令时,语气由should （应该1 had better最好\ must （必须）渐强八、had better表示”最好had better相当于一个助动词,它只有一种形式,它后面要跟动词原形had better do sthhad better not do sthIt is pretty cold. Youd better put on my coat.Shed better not play with the dog.had better have done sth表示与事实相反的结果,意为”本来最好”You had better have come earlier.九.would rather表示”宁愿”would rather dowould rather not dowould rather... than・・・宁愿而不愿还有 would sooner, had rather, had sooner 都表示"宁愿”.”宁可”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・典型例题--Shall we go skating or stay at home?-—Which do?A. do you rather B・ would you rather C・ will you rather D・ should you rather答案Bo本题考查情态动词rather的用法f would rather +do sth意为”宁愿M ■本题为疑问句,would提前,所以选Bo十.will 和 would注意:定搭配。

1 ) would like ; Would like to do = want to 想要Would you like to go with me?2 ) Will you...? Would you like...?表示肯定含义的请求劝说时f疑问句中 般用some,而不是anyoWould you like some cake?3 )否定结构中用will ,—般不用would, won*t you是一种委婉语气Won*t you sit down?十一、情态动词的回答方式问句肯定回答否定回答Need you...? Yes,。