6-情态动词

情态动词定义：情态动词表示说话人的语气、情绪和态度，认为‘可能’、‘应当’、‘必要’等等。

本身词义不全，不能单独作谓语，必须与后面的动词原形一起构成谓语。

情态动词没有人称和数的变化，有的情态动词有过去式。

常见的情态动词有can, could, may, might, must, have to, shall, should, will, would, ought to, need, dare, used to。

考纲解读：情态动词的基本用法（5年2考）掌握情态动词的基本意义及用法，把握情态动词表示推测、请求、许可等的异同，熟知情态动词后接完成时的含义。

1．can, could的用法》》品例句，得结论《《I can speak English, while I can’t speak Japanese.He could read books in English when he was only five.Man cannot live without air.①表示能力，可理解为能、能够，could是can的过去式。

注意：can与be able to的区别：两者都可表示能、能够。

can无人称和数的变化，过去式为could；be able to有人称、数和时态的变化。

can泛指一般的能力或一种客观可能，而be able to更加强调通过后天的学习和努力获得的能力，或者在某个场合和背景下，具体做到了某件事。

Edison always wondered why hens could hatch chickens while he was not able to.A big fire broke out in ABC hotel yesterday. Luckily, everyone was able to run out of the building. 在第二个例句中was/were able to do sth.相当于managed to do sth. /succeeded in doing sth.-I feel so bored.-You can watch TV.Could/Can you wait a few days for the money?-Could/Can I use your bike?-Yes, you can. / No, you can’t.②表示请求、建议、允许、许可，用could 比can语气更委婉(回答用can)。

He’s such a nice person that he can’t commit the crime.Can it be true？How can you be so careless!③在否定句、疑问句和感叹句中，表示怀疑、惊异、不相信的态度。

You cannot be too careful.I couldn't but choose to wait.The importance of reading can’t be stressed too much.④惯用形式，总结：cannot(can't)…too…/too much/enough无论怎么……也不(过分)cannot/couldn't help but do…; can do nothing but do…; cannot/couldn’t but do…不得不；只好can’t help doing…情不自禁……can’t help (to) do…无法帮助……He is in hospital. He can't be at school.He can’t /couldn’t have finished the task all alone.Can he be free now？It can be quite cold in the autumn.⑤在否定句和疑问句中，表示对现在的状态、现在正在进行的动作和过去的推测。

用于否定句，意为不可能。

用于疑问句，意为会不会。

can’t/couldn’t have done意为过去不可能做过某事，其反义形式为must have done。

在肯定句中，表示理论上如此，现实中不一定。

2．may, might的用法》》识规律，辨真伪《《①表示允许、请求。

Might/May I…？might比may语气更为委婉和有礼貌。

—May I ask you a question?—Yes, please.—May I watch TV after supper?—Yes, you may/can.或No, you may not./No, you can’t./You'd better not./You mustn't.(强烈的禁止语气)②惯用形式，总结：may/might as well do 不妨做……，最好；相当于had better domay well do 很/极可能may well not do 很可能不may… but…尽管……但是……You may as well go back home early.He may be lazy, but he can work very hard when he feels like it.③表示祝愿(不用might)。

采用部分倒装语序：May＋主语＋动词原形＋其他！May you be happy every day!May you succeed!④may 用于肯定句和否定句中，表示对现在的状态、现在正在进行的动作和过去的推测。

may/might have done表示过去可能做过某事。

(1)用于肯定句，意为“也许，可能”，might 的可能性比may更小。

He has a car. He may come by car, but I am not sure.He might have watered the flowers, for there is less water in the tank, but I am not sure.(2)用于否定句，意为“也许不/没有，可能不/没有”。

It is raining so hard. My friend may not come.Exercises:翻译：①-那个女孩是玛丽吗？-那个女孩不可能是玛丽，玛丽去了美国。

②-那个女孩是玛丽吗？-那个女孩可能不是玛丽，玛丽今天好像穿了红色的衣服，但是我不确定。

③你最好给你的父母打个电话，他们现在极有可能非常担心你。

④愿我们友谊长存！3．must，have to的用法》》识规律，辨真伪《《①must 表示“必须”，强调主观看法，只有现在时形式，否定式是must not (mustn't)，表示“禁止，不准”。

Everybody must obey the rules.You mustn't speak like that to your mother.—Must I hand in the composition tomorrow?—Yes, you must./No, you needn’t. /No, you don’t have to.[温馨提示1] 当must作“必须”意义讲时，其反意疑问部分用needn't;当含有mustn't时，其反意疑问部分用must/may。

You must go now, needn't you?You mustn't smoke here, must/may you?[温馨提示2]have to表示“必须，不得不”，着重强调客观需要，能用于更多时态(现在、过去和将来)。

I have to pick up my children.I had to leave at that time.The students of today will have to know how to use the computers of tomorrow.②用于肯定句，表示有把握的推测，意为“一定，肯定”。

表示对现在的状态、现在正在进行的动作、过去的动作的肯定推测。

否定式为can’tThis must be your pen. →must do/be 现在→否定：can’t do/ beHe must be doing his homework now. →must be doing 正在→否定：can’t be doingHe must have arrived already. →must have done 过去→否定：can’t/couldn’t have done[温馨提示]当情态动词must表推测时，反意疑问部分助动词的使用要根据情态动词后面所隐含的时间来确定You must be hungry now, aren't you?You must have heard about it, haven't you?You must have watched that football match last night, didn't you?③must 有“偏要，硬要”之意。

常出现于if you must do…固定句型中。

If you must leave, do it quietly.Must you make a noise like this?④a must: 必须做的事；必需之物A warm coat is a must in the cold winter.Patience is a must if you want to do your job well.Exercises:翻译：①-那个女孩是玛丽吗？-那个女孩一定是玛丽，只有她的头发是红色的。

②你偏要半夜弹钢琴吗？③我今天必须交作文，是吗？选择：①（2014·安徽合肥市第一次质检）They have been training very hard the whole season, and they C win this match.A. mightB. mayC. mustD. should②（2014·安徽皖南八校第一次联考）As a well-known Chinese saying goes, “If you want to be rich, you B first build roads.”A. mayB. mustC. canD. will③（2010·安徽，32）Jack described his father, who D a brave boy many years ago, as a strong-willed man.A. would beB. would have doneC. must beD. must have done4．will，would的用法》》试真题，得规律《《(江苏卷) Days later, my brother called to say he was all right, but C say where he was.A. mustn’t B shouldn’t C. wouldn’t D. mightn’t①用于各种人称，表示意志或决心。