语法专讲之情态动词

语法专讲之情态动词一、综述情态动词有一定到意义，但不能独立作谓语，往往和后面到动词原形一起构成谓语部分。

二、分类一）can, can’tcould, couldn’tbe able to二）should, shouldn’t;must, mustn’t;have to, don’t have to;ought to, ought not to三）need, needn’t;dare; dare notshall; shan’twill, would四）情态动词+ 完成时三、高考试题引入：1. —Do you know where David is? I couldn’t find him anywhere.—Well，he have gone far—his coat’s still here.A. shouldn’tB. mustn’tC. can’tD. wouldn’t2. My MP4 player isn’t in my bag. Where I have put it?A. canB. mustC. shouldD. would3. —She looks very happy. She have passed the exam. —I guess so. It’s not difficult after all.A. shouldB. couldC. mustD. might4. Helen go on the trip with us，but she isn’t quite sure yet.A. shallB. mustC. mayD. Can四、情态动词详细归纳：一）can、could与be able to1. 表示能力e.g. Most of us can use the computer now, but I couldn’t use it last year.e.g. He was not able to climb up on the top of the mountain.e.g. He was able to go to the party yesterday eveningin spite of the heavy rain.2. 表示客观的可能性e.g. Sometimes the temperature in Wuhan can fall to ten degrees below freezing.e.g. It can be quite windy in Wuhan, especially in spring.3. 表示推测。

多用于否定句和疑问句中。

e.g. He can’t be our head teacher as he has gone to Shanghai for a meeting.对比：e.g. He may not our head teacher as he said he has gone to Zhengzhou for a meeting.总结：can’t 不可能（语气最肯定）；well may not 很可能不（语气比较肯定）；may not可能不（语气最不肯定）4. 表示惊异或怀疑，常用语疑问语气。

e.g. 那怎么会是真的呢？How can it be true？e.g. 这到底是什么意思？What on earth can this mean?5. 表示请求，常用could 语气更委婉。

e.g. ---Can I go now?--- Yes, you can. / No, you can’t.e.g. --- Could I come to see you tomorrow?--- Yes, you can. ( No, I’m afraid not. )e.g. Could you wait a few days for the money?e.g. Could you be here at eight o’clock tomorrow morning?6. 在将来时和完成时中只能用be able toe.g. 我确信我很快就能得到那份工作。

I am sure I will be able to get this job soon.e.g. 他们已经能够按时完成任务了。

They have been able to finish the work on time.7. 表示经过努力而成功地办到某事，用be able to，这里beable to 相当于：succeed in 或manage toe.g. 经过几年的努力，他终于通过了考试。

After years of hard work he was able to pass the final exam.8. can’t wait表示“急于做某事”相当于be eager to ----e.g. I can’t wait to read this story book.我非常渴望读这本故事书。

e.g. I couldn’t wait to see her.我渴望见到她。

9. can not ---- too----表示“再----也不为过”；“越---- 越好”。

类似的用法还有：can never ---too---;e.g. We can not be too careful in doing experiments.e.g. Drinking water can never be clean enough.e.g. I think it right that one can not learn too muchknowledge.e.g. We can not praise him too much.二）、may 与might1. 表示“允许”；“可以”e.g. --- May I ask you a question?--- Yes, please.e.g. --- May I watch TV after supper?--- Yes, you may.(or No, you’d better not.)e.g. Might I use your telephone? (比用may语气更婉转)2. 表示可能性的推测含有“或许、大概或可能”的意思（多用于肯定句中）. 用might 代替may 时，语气将显得更加不肯定。

e.g. 我听说可能还留有几本书。

I hear there may be a few books left.e.g. 他明天或许会来。

He might come tomorrow.3. 表示期望或祝愿e.g. May you succeed!e.g. May you have more days as happy as this one! 三）、must 与have to1. must 表示“必须、应该”。

强调主观看法，只有现在时。

其否定形式为: mustn’t以must 开头的疑问句，其否定回答用needn’t 或don’t have to。

e.g. I must learn another language. (主观想法：I want to----)e.g. I have to learn another language. (客观所需，如：作为一个外交官)e.g. You must not smoke here!e.g. --- Must I do it at once?--- No, you needn’t. (---- Yes, you must.)e.g. The play isn’t interesting, I really must go now.e.g. I had to work when I was your age.2. must 表示必然的结果。

e.g.人固有一死。

All men must die.e.g. 如果你不快点，你肯定会错过火车的。

If you don’t hurry, you must miss the train.3. must 表示肯定推测, 多用于：must be 和must havedone短语中。

e.g. You’re Tom’s good friend, so you must know what he likes best.e.g. You must be hungry after your long walk.e.g. You must have left your bag in the library4. must 在反义疑问句中的用法：1）must 作“必须”解时，反义疑问句任用must。

e.g. 所有的孩子必须尊敬父母，不是吗？All the children must respect their parents, mustn’t they?2) must 表示“有必要”的含义时，反义疑问句用needn’t。

e.g. We must tell her the news, needn’t we?3）must be 表示“推测”时，反义疑问句用be 的适当形式。

e.g. He must be thirsty, isn’t he?4) must have done 表示“推测”时，用have 的适当形式。

e.g. He must have finished the work, hasn’t he?5. have to 一般表示客观原因所引起的“不得不---；必须---”。

其后面接动词原形，但是have to 有人称，单复数及时态的变化。

单三形式为has to; 过去式had to.e.g. We have to clean our classroom this afternoon.e.g. Mr Green has to work on the farm all day.e.g. He had to look after his younger sister yesterday. 四）、should 与ought to1. should 作为情态动词和ought to 在词义上很接近，但should 侧重于主观上的“应该”；而ought to 侧重于客观上的“应该”。

e.g. You ought to go and see your mother in the hospital tomorrow。

e.g. I think you should tell your mother the good news.2. should 可以表示语气较强的假设，意思是“万一”。