情态动词讲解

1、高一英语 情态动词1. can(1.) 能力 He can speak fluent English. 区别 can 与 be able to 的用法： can只有一般现在时与一般过去时；be able to有各种时态 be able to 表示经过努力设法做成某事，相当于 manage to do/succeed in doing Everyone was able to escape from the burning building.(2. ) 客观可能性(肯定句) “有时会”It can be quiet cold here at night.(3.)请求许可could (委婉语气)C

2、an I have a look at your new pen?- Could I use your computer tomorrow? - Yes, you can./No, Im afraid not.(4.) 用在否定句、疑问句中表怀疑，惊讶等Can it be true?How can you be so crazy?cant help doing sth. 忍不住做某事，情不自禁做某事I canthelp thinking he knows more than he has told us.can not/nevertoo再也不为过，越越好You cannot be too ca

3、reful when you drive a car.2. may(1.) 请求许可 might (委婉语气)- May I smoke here?- Yes, you may./No, you mustnt.(2.) 可能性 John is absent. He may be ill.It may be not true./It can tbe true.(3.) 用于祈使句中表祝愿May you succeed!may/might as well (do sth.) 做某事倒也无妨，只好做某事If no one else wants it, we might as well give it

4、 to him. may well do sth. 完全可能 They may well win.3. must(1.) 必须 Soldiers must obey orders.区别 must 与 have to 的用法： must表示主观看法，have to表示客观需要I feel I must call you to thank you for your help. Its raining heavily. You have to take an umbrella. must无时态变化，have to的时态随have的变化 否定形式的含义不同：mustn 表示禁止，don have to

5、表示不必You mustnttake the book out of the reading room.You donthave to tell him the truth if you don t want to. 回答 must 问句 - Must we hand in our exercise book today?-Yes, you must./No, you don have to/needn(2.)偏偏，偏要Must you shout so loudly ?If you must (do sth.)(表示虽不赞同但可允许)如果你一定要做某事-May I smoke here ？-

6、If you must, choose a seat in the smok ing sect ion.归纳：can, could, may, might, mus都可以表推测肯定句 f must, may, mighty否定句 f cant, couldnt (不可能)，may not (可能不)疑问句 f can, could情态动词+do/be表现在y情态动词+be doing表现在进行、将来J情态动词+have done表过去如何运用在反意疑问句中：反意疑问部分中的助动词必须根据陈述句中去掉表推测的情态动词，改为陈述客 观事实的陈述句中的谓语动词来判断(可根据时间状语)。(1.) He

7、 may know the pla n,?(2.) He must have lived here for a long time,?(3.) He can have left yesterday,?4. shall(1.)用于一、三人称，表征求对方意见Henry is wait ing outside. Shall he come in, sir?(2.)用于二、三人称，表说话者对主语的命令、规定、允诺、威胁、决心等The stude nts shall wear uni forms.You shall get an an swer from me tomorrow.5. should(1.

8、)应该，表示劝告、建议，相当于ought to (语气稍强，客观情况)As stude nts, we should work hard.Every citizen ought to obey the law.(2.)按道理应当There are many hotels there. There should n tbe any difficulties for you to find one.(3.)用于表示感情的形容词后的that从句中表竟然It is ast onishing that he should be so rude to you.(4.)在 why, how, who, wh

9、at + should sb. do 结构中表惊讶，恼怒等Why should I help him? He t never done anything for me.(5.)(表示可能)万一，假如The company guaranteed free after-sales service , should their products have any risk in safety.If you should cha nge your mind, do let me know.6. will(1.)意愿(现在)would (过去)If you will liste n to me, I t

10、l give you some advice.They wouldn tlet him in because he was poorly dressed.(2.)用于第二人称，表请求would (委婉语气)Will/Would you please pass me the book?(3.)习惯性动作(现在)would (过去)Fish will die without water.When we worked in the same office, we would ofte n have coffee together.区别 would与used to do/be的用法：would表示过去

11、反复发生的动作，与现在无关；used to do/be表示过去的状态，强调现在与过去的对比。He used to be a n aughty boy.When he was young, he would smoke a lot.(4.)功能性，倾向性 The door won open.归纳：must, will, ought to, should, can, could, may, might都可表示可能性。表示可能性大小的顺序为 mustwillought toshouldcancouldmaymight7. need作情态动词，用于 否定句、疑问句 中 need do sth.need

12、 not do sth.-Need we leave soon?-Yes, you must./No, you needn 作实义 动词 need/needs/needed to do sth.don /doesnt/didn need to do sth.need doing = need to be done (require/want) 某事需要被做This shirt n eeds wash ing/to be washed.8. dare作情态动词，用于 否定句、疑问句 中 dare/dared do sth.宀 dare/dared not do sth. -Dare you te

13、ll her the truth?-Yes, I dare./No, I dare not.作实义 动词 dare/dares/dared to do sth.don does ndid n dare to do sth.I dare say 我想，很可能，大概I dare say you know about it already.归纳：情态动词+have done的用法：1. must have done肯定已经做了某事宀 主要用于陈述句中（推测）Y may have done可能已经做了某事宀 主要用于陈述句中，偶尔用于否定句中gan have done可能已经做了某事宀主要用于疑问句和否定句中2. rshould （not