Modal动词用法

Modal动词用法 Ⅰ情态动词的类型

① 只做情态动词的有：can(could),may(might),must, ought to ② 可做情态动词也可做实义动词的有：need,dare ③ 可做情态动词也可做助动词的有：shall(should),will(would) ④ 具有情态动词的某些特征的有：have(had)to,used to Ⅱ 具体用法

㈠ 表能力（can,could.be able to）

⒈表现在或一般的能力,一般能力即无论什么时候想做就能做到的能力.can比

be able to 更普遍。can (客观能力)；be able to(主观能力)。 Eg.I can’t pay you today;Can you wait till tomorrow ? I am able to finish my homewoek on time. ⒉ 表将来的能力 （will be able to）

Eg.If you have a good sleep,you will be able to work out this problem. ⒊ 表过去的能力

Could + v原形 表示过去一般的能力，但不表示做或未做某事 Could have done 表示过去有能力做但未做。

Was/were able to=managed to do sth=succeed in doing sth 表示过去有能力做且成功做了某事。

Eg.She could/was able to sing like an Angle when she was a child. I could have worked out the problem,but I did’t. ㈡ 表推测（可能性）

⒈客观可能性常可以说明人或事物的特征。但并不涉及具体某事是否会发生。

Eg.It’s usually warm in my hometown in March,but it can be rather cold sometimes.

Eg.Peter can be really difficult at times even though he is a nice person in general. ㈡ 具体事情发生的可能性

may,must→肯定句 may→否定句（可能不） must→否定句（禁止） can→否定句（不可能），疑问句，感叹句。 肯定句（理论上的可能性） could →肯，否，疑问句

Eg.①How can you be so stupid ?

②This can’t/could’t be done by him.(don’t believe) ③This may not be done by him.(not certain) Would,could should,might 不一定与过去时间有关 ㈢表请求，允许，允诺

① Shall/may(might)/can(could) I/we...? Shall he/she/they...? Would/will you...?

(用于一，三人称的疑问句，表请求或提出建议)。 Eg. Shall we begin our class?

Shall the driver wait outside? Would you do me a favor?

②you/he/she/they shall...（用于二，三人称肯定句，表命令，警告，允诺，威胁， 或当颁布，法律，规定时）。 Eg.He asked me for this book many times,please tell him he shall have it tomorrow.

It has been announced that candidates shall remain in their seats until all the papers have been collected. ③ would/should/could/might 表委婉的功能。 ㈣ 表示必要性。

① must +v (表示现在或将来必须做某事)。

must be (表示现在或将来一定做某事)。

must have done (表过去想必，准是，一定做了某事)。 Eg.You must go now.

You must be a good secretary in future.

The lights were out,so they must have been asleep ② don’t have to do sth

don’t need to do sth (表现在或将来不必做某事) needn’t do sth

③ didn’t have to do sth

didn’t need to do sth (表示过去没必要做某事，而不涉及是否做)。 ④ needn’t have done sth (过去没必要做某事，但事实上却做了)。 ⑤ should +v

should have done (过去本应该做某事而未做)

㈤ 情态动词+have done

can have done (否定句，疑问句) eg.He can’t have forgotten it. Can he have gone to his aunt’s? Could have done (肯，否) eg. You could have done better,but you were too careless. I saw Mr wang just now.He couldn’t have gone to

Beijing.

may have done (肯，否) eg. It’s too late.I think he may have gone to bed. He may not have finished the work.

might havee done (肯) 含有轻微的责备。Eg. You might have give him more

help,though you were busy.

should/ought to have done needn’t have done ㈥ 特殊用法

⒈may 用于祈使句表示祝愿

Eg.May you reyurn in safety. 2.must 偏要，硬要，坚持做某事。 Eg. Must you make so much noise? 3.should 竟然，竟会。（表不能理解，感到意外，惊异） Eg.Why should you be so late today?

4.can(could) not/never do...enough(too+adj) Eg.I can’t thank you enough.

5.can’t but do sth= can’t choose but do sth

have no choice but to do...

(不得不，只好。别无选择不得不做...)

Eg. We can’t but respect their decision.

6.may well +v =be very likely to do...(完全能，很可能) may as well+v(最好，倒不如)

eg. He may well be proud of his girl. You may as well do it at once.

虚拟语气

虚拟语气表示说话人所说的话不是事实，而是一种假设，愿望，怀疑或推测。 Ⅰ 在条件句中的用法

⒈与现在事实相反 if+S+｛did/were...｝,S+would/should/could/might+do... ⒉与将来事实相反 if+S+｛did(were)/were to do.../should do...｝

S+would/should/could/might+do...

⒊与过去事实相反 if+S+had done...,S+would/should/could/might+have done... Ⅱ使用虚拟条件句时要注意以下几点： ⒈错综时间条件句：当条件状语从句表示的行为和主句表示的行为所发生的时间不一致 时。

Eg.If you had followed my advice just now,you would be better now. If you had studied hard before,you would be a college student. ⒉if 省略句

在条件句中可省略if,把were,had ,should提到句首，变为倒装句式。 Eg.If I were at school again,I would study harder. If you had come earlier,you would catch the bus. If it should rain tomorrow,we would not go climbing.

⒊ 用介词短语代替条件状语从句。常用的介词有with,without,but for. Eg.What would you do with a million dollars? = What would you do if you had a million dollars?

Without your help,we couldn’t have finished the work ahead of time. =But for your help,...

=If it had not been for your help,... =Had it not been for your help,.. 4.含蓄条件句

有时为了表达需要，在虚拟语气中并不总是出现If 引导的条件句，而通过其他手段替 条件句

Eg.I was ill that day.Otherwise,I would have taken part in the sports meet. Ⅲ.在名词性从句中的用法。

1. 在wish宾语从句中。⑴ I wish +s +did/were

+s +had done... insist）; +s+ would/could/might do...

2.用于表示建议，愿望，命令 等词后的宾语从句中。常见v 为：一个坚持(insist);两个命令（order/command）;三个建议（advise/suggest/propose）;四个要求（demand/require/request/ask）,从句的虚拟语气结构为“(should) +do...”

Eg.He suggested that we (should) start off early the next day. They insisted that the boy (should) go with him.

3.在would rather宾语从句中：would rather +s+ did (对现在或将来虚拟) +s+ had done(对过去虚拟)

4.在主语从句中：It is desired/suggested/proposed....+that + s + (should) do... Eg. It is suggested that the meeting should be put off till next week.

5.在表语从句和同位语从句中，在suggestion,proposal,,order,request,advice等名词后的表语从句和同位语从句中，从句的谓语为(should) +v

Eg.We all agreed to his suggestion that we should go to Dalian for sightseeing. 6.在as if/as though的状语从句中，与wish 从句中的变化一样。 Eg. He looks as if he were an artist.

She speaks English so fluently as if she had studied English in America. He learns English so hard as if he would go to the U.S.A. 7.虚拟语气在定语从句中。

It’s (high) time (that)sb +did/should do...用来表示提议。 Eg.It’s (high)time that you went to school. It’s (high)time that we should start out. ‘

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