情态动词精讲(全)

情态动词精讲

Modal Verbs

情态动词是一种本身有一定的词义，但要与动词原形一起使用，给谓语动词增添情态色彩，表示说话人对有关行为或事物的态度和看法，认为其可能、应该或必要等。

基本助动词与情态助动词（两种助动词）最主要的区别之一是，基本助动词本身没有词义，而情态助动词则有自己的词义，能表示说话人对有关动作或状态的看法，或表示主观设想。

牢记的两句话：

肯定句中一定没有can have done的形式；

Mustn’t have done无论如何都不存在。

可以表示虚拟的情态动词：could ,might, should, would, need

可以表示推测的情态动词：could, might, should, must, may, can(否，疑)

（虚拟与事实相反，推测与事实相一致）

综述：

情态动词表推测的用法小结

（一）情态动词表推测的三种句式

1.在肯定句中一般用must (一定)，may（可能），might / could（也许，或许）, should (按理说应该)；

（1）He must/may/might know the answer to this question.

他一定/可能/也许知道这个问题的答案。

（2）It is cold in the room. They must have turned off the heating.

屋里很冷，他们肯定把暖气关了。

（3）It’s seven o’clock. Jack should/ought to be here at any moment.

现在七点钟了，杰克理应随时到达。（推测）

2.否定句中用can’t / couldn’t(不可能), may not/might not(可能不)，shouldn’t (按理说应该不)；

（1）It can’t/couldn’t be the headmaster. He has gone to America.

这不可能是校长，他去美国了。

（2）He may not/might not know the scientist. I’m not sure.

他也许不认识那位科学家。

（3）Since you have made so many preparations for the exam, there shouldn’t be any difficulty for you to pass it.

既然你为考试做了这么多准备，按理说通过应该不会有任何困难。

3.疑问句中用can/could (能……?)。

（1）Could/Can he have finished the task?

他可能把任务完成了吗？

（2）I can’t find my wallet anywhere. Where can/could I have put it? Could/Can I have lost it?

注：以上三种句式中情态动词的语气按程度都是依次递减的。Might, could并非may, can的过去式，而表示语气较为委婉或可能性较小。

（二）情态动词表推测的三种时态（情态动词本身并无时态差别）

1.对一般现在、将来情况的推测，用“情态动词+ do”。

（1）He can’t ( couldn’t ) / may ( might ) not be at home at this time.

这个时候他不可能/可能不在家。

（2）She must / may / might / could arrive before 5.

5:00前她一定/可能/也许到。

2.对现在进行或将来进行的动作进行推测，用“情态动词+be doing’。

He must / may / might / could be listening to the radio now/this moment tomorrow.

他一定/可能/也许正在听收音机。/ 明天这个时候…

3.对过去情况的推测，用“情态动词+ have done”。

（1）It must / may / might / could have rained last night .The ground is wet.

地湿了，昨晚肯定/可能/也许下雨了。

（2）The door was locked. He can ( could ) not / may ( might ) not have been at home .

门锁着，他不可能/可能不在家。

（3）Can / Could he have gotten the book？

难道他找到书了吗？

4.对过去进行的动作进行推测，用“情态动词+ have been doing”(也可表示对从过去开始到现在一直在进行的动作进行推测)。

--You must have been driving at seventy miles an hour. Didn't you see the speed limit?

--I can't have been. I was doing eighty when I overtook you.

--I must have been dreaming.

情态动词的基本用法：

1.must

1). “必须” （命令，义务）

You must work hard if you want to succeed. “必须，一定要”

You mustn’t play with fire! “禁止，不许”

--Must I finish my homework right now?

--Yes, you must. / No, you needn’t/don’t have to.

2) “非得”（坚持）

--Must you make so much noise? I cannot concentrate.

--May I smoke here?

--If you must, choose a seat in the smoking section.

3) “一定是” （推测）

He must be in the room, for the light is still on.

He cannot/couldn’t be in the room, for the light is off. (否定形式)

They must have seen us yesterday, didn’t th ey?

They must have seen us (before), haven’t they?

2.can/could