2019-2020学年中考英语语法备考秘诀 — 情态动词
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1） 情态动词不可以表示正在发生或已经发生的事情，只表示期待或估计某事的发生。
2） 情态动词除ought 和have 外，后面只能接不带to 的不定式。
3） 情态动词无人称，数的变化，即情态动词第三人称单数不加-s。
4）情态动词没非谓语形式，即没不定式，分词，等形式。
容易见到的情态动词有：can ,may , must ,shall , will , dare , need等,另外,have to、had better也当作情态动词用。情态动词后面需要加动词的原形。
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1．情态动词也是“辅助兴”动词，用来表示说话人的语气或情态。情态动词所表示的情态有：请求、命令、许诺、可能、需要、敢于、愿望、义务、能力等。
2．情态动词本身有词义，但词义不完全，不可以单独用作谓语，无人称和数的变化，且后面只跟动词原形。如：
她会唱英文歌曲。
She cans sing an English song.（F）
She can sings an English song.（F）
She can sing an English song.（T）
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与原形相同的有：
must --- must ought to --- ought to
与原形不一样的有：
can --- could will --- would
may --- might shall --- should
need --- needed dare --- dared have to --- had to
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（二）情态动词的类型：（见下表）
原 形 | 过去式 | 词 义 |
can | could | 能 |
may | might | 可以（可能） |
must | must | 需要（不能不） |
will | would | 想 |
shall | should | 应该 |
need | needed | 需要 |
dare | dared | 敢于 |
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cannot --- can’t could not --- couldn’t may not--- mayn’t
might not--- mightn’t must not --- mustn’t will not --- won’t
would not --- wouldn’t need not --- needn’t shall not --- shan’t
should not --- shouldn’t ought not --- oughtn’t dare not --- daren’t
（二）情态动词
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1．can与could
1）． can
（1）表示体力或脑力方面的“能力”，也能表示依据客观条件能做某事的“能力”。
He can drive.
Can you jump as far as he did?
I can’t catch up with Jim.
can与be able to二者都表示“可以”，不同是：can只有目前时和过去式，而be able to可用于各种时态。如：
I’ll be able to speak French in half a year.
He hasn’t been able to finish it on time.
（2）表示允许：
You can go now.
Can I use your bike?
（3）表示推断：
Who can it be?
It can’t be true.
can表示猜测或怀疑只用于疑问句及否定句中。
can 和be able to
1）can/could 表示能力；可能 （过去时用could）, 只用于目前式和过去式（could）。be able to可以用于各种时态。比如：
They will be able to tell you the news soon. 他非常快就能对你说消息了。
2）只用be able to的状况：
a. 坐落于助动词后。
b. 情态动词后。
c. 表示过去某时刻动作时。
d. 用于句首表示条件。
e. 表示成功地做了某事时，用was/were able to，不可以用could。比如：
He was able to flee Europe before the war broke out. = He managed to flee Europe before the war broke out.
他在战争爆发之前逃离欧洲。
注意：could有时不表示时态
1）提出委婉的请求，（注意在回答中不可用could）。比如：
--- Could I have the television on? 我能看电视吗？
--- Yes, you can. / No, you can't. 可以/不能。
2）在否定句、疑问句中表示推断或怀疑。比如：
He couldn't be a bad man. 他不大可能是坏人。
2）． could
（1）can的过去式，表示过去有能力及过去的可能性。
He couldn’t climb up the mountain.
The news could be true.
（2）表示客气地请求或委婉地陈述建议。
Could you go skating with me tomorrow?
I’m afraid I couldn’t give you an answer tonight.
（3）表示惊异、怀疑、不相信等态度
How could he say that?
He couldn’t be in Beijing.
2．may与might
1）． may
（1）表示请求、许可、可以
—May I use your dictionary?
—Yes, please/certainly.
May I come in?
（2）表示推断说话人的猜测，觉得某一事情“可能”或“可能”发生。
It may rain this afternoon.
I may leave for Hangzhou next week.
（3）may用于感叹句中可以表示祝愿或愿望。
May you do well!
May you have a good time!
2)． might
（1）用作may的过去式。
We didn’t know that he might be our new teacher.
The accident might happen the day before yesterday.
（2）替代may来表示目前时间的动作，主要于推断（但其可能性比may更低）。
I’m afraid it might snow tomorrow.
You might meet him at the conference.
The movie might have finished now.
（3）委婉地表示请求（不是过去式）。
Might I ask you a question?
Might you go there with me?
3．must
（1）．表示义务，命令或必要。
Soldiers must obey orders.
We must be strict with ourselves.
（2）．表示一定的推断：肯定
He must be at home.（对目前的猜测）
I think you must have made a mistake.（对过去的猜测）
He must be our new teacher.
He can’t be our new teacher.
（3）除此之外还要弄了解must与have to有什么区别
4．will与would
1）． will
（1）表示意愿、决心。此时可用于各种人称。
He won’t come to see you.他不愿来见你。（表示意愿）
I will try my best to catch up with her.我将尽最大努力赶上她。（表示决心）
（2）表示请求，此时仅限于“will you …？”句型中，仅用于第二人称和疑问句中。
Will you please buy me an English-Chinese dictionary when you go to the bookstore?
Will you have some rice?
2）． would
（1）will的过去式，表示过去的意愿和决心。
He said he would do everything for her, but she said she would never see him again.
They believed that we would help them.
（2）用于目前时，表示委婉地提出请求，建议或怎么看。此时would的使用方法比will愈加委婉。
Would you please show me the way to the museum?
I would like to say something about it.
will和would用于“劝某人同意……”时，只可以用some，不可以用any。如：
Would you like some fish? 吃点鱼怎么样？
5．shall与should
1） shall
征求他们建议或请求，用于1、三人称。表示“需不需要……？”、“……怎么样？”
Shall I open the window?
Shall the doctor come?
2） should
（1）should意思是“应该”，表示劝告或建议（=ought to）
You should wash your hands before dinner.
We should help each other.
（2）用来表示可能性或猜测。
He should be in the office now.
I should be right.
（3）should有时能表示说话人的情感等。
It’s funny that they should be confident.（表示轻视）
Why should I do that for you?（表示不满）
（4）should后接动词不定式（不加to）时，若用于一定句，表示某件事本应该完成却没有完成；若用于否定句，则表示某事不该发生却发生了。
You should have told us the truth.（应该告诉却没）
He should have known the importance of it.应该了解却不了解）
We shouldn’t have left so early.（不应该早出来，可已经做了）
6．need
1）need意思是“需要，需要”，主要用于否定句和关系问句中。
You needn’t come so early.
Need I take part in the Party?
2) need引导的疑问句，一定回答时多用must，否定回答时用needn’t。
Need he come?
Yes, he must.
No, he needn’t.
3) need后接名词做宾语时，表示“需要”某件事物，此时用作实义动词，与普通的实义动词使用方法完全一样。如：
We need three apples.
He doesn’t need so many books.
7. ought
ought只有一种形式，后面常与to连用，意思是“应该”。
You ought to visit us often.
Sorry, I ought to leave now.
在表示“应该”时，ought to的语气比should要强，比must稍弱。
8. dare
1) dare意思是“敢”，用于一定结构中时，后接加to的动词不定式。
The boy dared to climb up the tree.
She should dare to question her teacher.
2）dare用于否定句或疑问句中时，与大部分的情态动词一样，后接不带to的动词不定式。
Don't dare do that again!
The poor girl dare not go home.
9．had better
You had better see a doctor.
You had better not leave now.
Had I better wait for her?
