情态动词重点讲解㈠情态动词的语法特征 情态动词主要有can, may, must, could, might, shall , should, will, would, ought to, need, dare等。 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,即动词原形。 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。
㈡情态动词表推测1. 形式 肯定的推测：must 可能的推测：may might can could 否定的推测：can’t couldn’t 疑问的推测：can could (注意mustn’t表“禁止”) 2. 时间 对过去：情态动词+完成式(have done)“过去可 能” ①must have done “过去一定做了某事” ②can’t/couldn’t have done “过去不可能做了某事” ③may/might have done “过去可能做了某事” 对正在进行：情态动词+be doing 对现在或将来：情态动词+do
不同的“肯定”程度可按下列层次排列： He is at home. (事实) He must be at home.(非常肯定的推断) He could be at home.(很可能) He ought to be at home.(很可能) He may be at home.(仅仅可能而已) He might be at home.(或许, 非常不确定) He might not be at home.(也许不在家) He may not be at home. (比might可能) He couldn’t be at home.(很可能不在家) He can’t be at home.(一定不在家) He isn't at home.(事实)
㈢情态动词+完成式①过去可能②表示“本…却…” might have done
“本来可以做某事”,含有轻微的责备语气。 should/ought to have done “本该做某事而未做”; should not/ought not to have done表示”不该做的事而做了” could have done “过去能做而没做”,有一种对过去为付诸实施的 事情的惋惜。 needn’t have done ”本来不必去做某事而做了” 注意：didn’t need to do表示“没必要做某事也没做 ” would rather have done 表示“当时宁愿做了某事”,其否定式would rather not have done表示相反的含义，两者都表示“后悔 ”之意
㈣高考常用情态动词辨析1. 能力 The parrot can speak three languages. 2. 推测，“可能”(否定、疑问句)This person can not be him. He has gone to Shanghai. 1. can 3. 允许 Can I borrow the book from the library. 4. “有时会” Shanghai can be very cold in March. could①(过去)有能力② (委婉)可能
1.Can 表示能力， be able to表示经过努力而做成了某事 2. can 与 be =manage to do/succeed in doing。 able to”能力” 2.在否定结构中，二者可互换 3. can/could + have +p.p 1.在否定、疑问句中表示对 过去的推测 2.
在肯定句中表 “本可以做 而未做”
1. The door was locked. She couldn’t have been at home. 2. You could have been more careful.
1. may
1. 没有把握的推测 2. 表示允许、可以 3. 表示祝愿
might 过去式；语气更委婉 1. She may be still waiting for us. 2. May I come in? 3. May you have a happy holiday. 短语：may/might as well do sth.不妨做某事 2. may/might + have +p.p 表示对过去动作的推测 1. He might have spoken to her yesterday. 2. You might have told me earlier.
1.表示肯定的猜测,但只用于肯定句 1. must 2. mustn’t 表示“禁止、不准许、不可 以” 3. 偏要、非要(表示与说话人愿望相反 或不耐烦) 1. must主观;have to客观 2. must ;have to 2.don’t have to 表示没有必要
3. must + have +done 对过去事情的肯定猜测。a. The road is wet. It must have rained last night.b. You mustn’t take photographs in here. It’s forbidden. b. John, look at the time. Must you play the piano at such a late hour?/ If you must smoke, do it outside.
shall
1.第一、三人称疑问句中表示“请求或征 求对方意见 Shall I get you a cup of coffee?/Shall he wait for you at the gate? 2.第二、三人称陈述句中①表允诺“会(得到)”If
you work well, you shall have higher wages. ②表命令、警告、威胁、决心 He shall do as I order. ③在法律/条约/协定文件中, 表义务、规定“应， 必须” The new law shall take effect next week.
1.(表惊讶、遗憾)竟然会It is surprising that he should have been foolish/ she should have lost all his money. 2.(表义务、责任、劝告、建议)应当，应该 Children should be honest to their parents. Young people should learn how to use computers. Should 3.(表示推测)用在肯定句中，意为“想必，大概， 或许” It should be a nice day tomorrow. Try phoning Robert, he should be home now. 4.(用于问句，表示询问、征求同意)可以、该 Should I turn on the light?/Where should I meet you tonight?
should/ought to have done表示本应该做而未做 You should have been here five minutes ago. You should have told me the news earlier, but you didn’t.
Will
1、表示意愿、决心或愿望I will make the computer work even if I have to stay up. 2、表示请求(用于第二人称)Will you give me a message when you see him? 3.(表示习惯性/倾向性/必然性)惯于/老是/总是 Accidents will happen./Boys will be boys.
would\used to do (1)would表示过去反复出现的动作，但不能表示过去存 在的状态，不能说：“she would be a quiet girl.” (2)would表示完全过去的事情，同现在没有联系。used to强调过去和现在的对比，现在已不这样 He used to be a naughty boy and cause trouble. Sometimes she would take a walk in the woods.
情态动词在一般疑问句中的回答：
Yes, I can. ① Can you sing? No, I can’t. Yes, you may. ② May I come in? No
, you mustn’t.③ Must I hand in the book now? Yes, you must. No, you needn’t /don’t have to. Yes, you must. ④ Need I finish it now? No, you needn’t.
