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1、情态动词1、can和could (could为can的过去式) 的基本用法(1)表示能力，如：He can speak English better than you. (2)在疑问句和否定句中表示“怀疑”、“猜测”或“可能性”，如：Can this green bike be Liu Dongs? (3)表示“许可”时can可以和may换用，如：You can (may) go home now. (4)用在肯定句中表示理论上的可能性，表示：“有时候会。”，如：A man who is in his nineties can be forgetful.(5)can和be able to都可表
2、示能力，两者在意思上没有什么区别。但是can只能有现在式和过去式，而be able to则有更多的形式，如：He will be able to do the work better.注意：were/was able to do sth.指过去做成了的事相当于manage to do/succeed in doing sth.With the help of the firemen, they were able to leave the burning house. 2、may和might (might为may的过去式)的基本用法(1)表示允许或征询对方许可，有“可以”之意，如：You ma
3、y use my dictionary. 当回答由may引起的问题时，否定答语要用must not表示“不可”、“不应该”、“不行”。-May I watch TV tonight? -Yes, you may(No, you mustnt/No, you cant/No, you had better not).(2)may或 might都表示可能性，表示“或许”、“可能”之意，如果用might表示可能性，则语气更加不肯定，用于肯定和否定句中，不用于疑问句。 They may (might) be in the library now .（3）may位于句首表示祝愿 May you succ
4、eed in the coming new year!3、must的基本用法 (1)must表示“必须”，其否定式 must not，缩写形式为 mustnt，表示“不准”、“不许可”之意，如： We must study hard and make progress every day. You mustnt touch the fire. - Must we finish the work tomorrow? -No, you neednt (dont have to), but you must finish it in three days. (2)在肯定句中must可以表示推测，表示
5、“一定”或“必定”之意，如：- Whose new bike can it be? - It must be Liu Dongs. I know his father has just bought him a new one.(3)表示一种与说话人愿望相反、不耐烦的感情色彩。表示“偏偏”; “非要”。如：-Could I have a word with you, mum? -Oh dear, if you must.(4) must着重主观看法，have to比较强调客观需要且使用于多种时态，“不得不”，如：When he was a child, he had to work to su
6、pport himself.4、can, could, may, must后接完成式的用法(1)can, could后接完成式的用法：在否定句或疑问句中表示对过去发生过的事情的“怀疑”或“不肯定”的态度，Could he have said so? 在肯定句中，可以表示过去可能做到而实际并没做到的事情，有“劝告”或“责备”的语气。如：- When did you answer her letter? - Only yesterday. - Its too late. You could have answered it earlier, I am sure. (2)may, might后接完成
7、式的用法 表示对过去某事的推测，如果使用might，语气就比较婉转或更加不肯定，如：Mary might have learned some Chinese before. 可以表示过去本来可以做到而实 际没有做到的事情，有“劝告”或“责备”的语气，如：You didnt do the work well that day. You might have done it better. (3)must后接完成式的用法：表示对过去某事的推测，认为某事在过去一定做到 了，如：Liu Dong isnt in the classroom. He must have gone to the libra
8、ry. 5、should/ought to的基本用法(l)表示根据某种义务或必要“应当”做某事，语气比should强，例如：Everyone ought to obey the traffic regulations. (2)表示推测，“应该会”，如：Its nearly seven oclock. Jack should be here at any moment. (3)“ought to/should+ have+ 过去分词”表示过去应做某事而实际未做。例如：You ought to have helped him. (but you didnt) 6、dare的基本用法 (l)dare
9、 (dared为过去式) 作情态动词用时，主要用于否定句，疑问句和条件从句中，如：Dared he break the traffic regulations again? (2)在现代英语中dare常用作行为动词，其变化与一般行为动词相同，如：She dares to stay at home alone at night.7、need的基本用法 (1)need作情态动词用时，主要用于否定句和疑问句中，如：He neednt worry about us now. (2)need也可作为行为动词用，可用于肯定句，否定句和疑问句中，其后可接名词、代词、动名词或带 to 的动词不定式为其宾语。如
10、：You need to practise reading aloud every day. (3)neednt后接完成式可以表示过去做了一件本来不必要做的事情，如：- Did you answer the letter yesterday? - Yes, I did. - But you neednt have answered it.8、shall的基本用法(1)shall用作情态动词时，用于第二、三人称，表示说活人的意愿，可表示“命令”、“警告”、“强制”、“威胁”或“允诺”等意， 如：He shall go first, whether he wants to or not. (2)在
11、疑问句中，shall用于第一、三人称，表示说话人的征询对方意见或请求指示，如：Shall I open the door?9、will的基本用法(1)用于各人称，可以表示“意志”或“决心”，如：I have told him again and again to stop smoking, but he will not listen. (2)在疑问句中用于第二人称，表示说话人向对方提出请求或询问对方的意愿，如：Will you please tell me how to get to the Capital Gymnasium? (3)will可以表示一种习惯性的动作，有“总是”或“会要”之
12、意，如：Every morning he will have a walk along this river.10、would的基本用法(1)would作为will的过去式，可用于各人称，表示过去时间的“意志”或“决心”，如：He promised he would never smoke again. (2)在疑问句中，用于第二人称，表示说话人向对方提出请求或许问对方的意愿时，比用will的气更加婉转，如：Would you like some more coffee?(3)would可以表示过去的习惯动作，比used to正式，并没有“现已无此习惯”的含义; used to后可以接表示动作
13、或状态的动词；而would后只能接表示动作的动词；used to不能接时间状语；而would可以接时间状语。如：Last year our English teacher would sometimes tell us stories in English after class. I dont swim as often as I used to.11、had better “最好”，后接不带to的不定式，例如： - We had better go now . - Yes, we had (wed better/ we had better). Hadnt we better stop now? (Had we better not stop now?) I think Id better be going.
