情态动词
情态动词是高考的重点考查项目，对学习情态动词的要求是：
首先、了解情态动词各自的基本意义及用法，然后掌握情态动词表示推测的用法（其中重点是对表过去推测的用法）还要注意带有情态动词的反意疑问句的用法。
情态动词的特征：
1.本身有词义，但完全。因此不能独立作谓语，只能和动词原形一起构成谓语。
2.后接动词不定式一律不带to
3.不随人称和数的变化。
情态动词各自的基本意义及用法
表一、can 与could用法对比表
对比点can could
1、表“能力”Can you lift this heavy box? I couldn’t understand what he said at
all.
2、表“许可”You can use a different material
instead.
He said I could borrow his bike.
3、“怀疑”No, no, it can’t be true.
What on earth can this mean?
We thought the story could not be true.
How could you be so careless?
4、can与be able to 区别1.could代替can，表示语气更为婉转。
Eg. Could I use your bike? Yes, I can
2.can (能够)=be able to(仅表能力时)，但be able to 表示一番努力后，才
能做得到，且有更多的时态。
He was a good swimmer, so he __________ swim to the river bank when the boat sank.
A. could
B. might
C. shall
D. was able to
表二、may与might用法对比表
对比点may Might
1．表“询问”May I …?(=Can I …?) Might I …?(=Could I…?)(但比用may
更客气)
2.表“允许”You may take the boy there. He told me he might come .(might 与
told相呼应)
3．表“可能”“或许”She may nor like this place. I’m afraid he might not like this play.
注： 1.May I…?的答语。
2.may可表示期望或祝愿
May you succeed !
3.may (might)用于目的状语
从句中肯定：Yes, you may.
否定：No, you mustn’t 不行（语气强硬）No, you may not 或No, you’d better not. The emperor gave them some gold in order that they might begin their work at once.
表三、must与have to的用法对比表
对比点must have to
1．表“必须”（主观看法）必须；没有过去
式，可用于间接引语中。He
told me I must do according to
what he said.
（客观需要）不得不，有多种时态。
It’s raining heavily, we can’t go now.
2.疑问句Must I …?
Yes, you must.（一定）
No, you needn’t./ you don’t
have to.(不必)
Do you have to go today?
Yes, we do.
否定句：You don’t have to worry about
that.
表四、need与dare的用法对比表
对比点need dare
1.情态动词+动词原形1）否定式
2）疑问式He need not (needn’t)go.
----Need we do it again?
---No, you needn’t do it again.
He dare not say so.
Dare she go out alone at night?
How dare you say I’m unfair?
If he dare do that, he’ll be punished.(条
件句)
I dare say.(固定用法)
2.行为动词+带to不定式1）肯定式
2）否定式
3）疑问式He needs to go.
He doesn’t (does not)need to
go.
Does he need to do it again?
No, he doesn’t need ot do it
again.
He dares to say.
He does not(doesn’t)dare to say.
If you dare to jump into the water from
here, so dare I .
3. did not need to do 表示过去没有必要做She didn’t need to attend the meeting yesterday, and she stayed with her children.(她没有参加)
表五、should与ought to用法对比表
对比点should ought to
1、表“应该”表劝告、建议
You should listen to the
doctor’s advice.
We should learn from Zhang
Hua
表示“有责任有必要”做某事
You ought to finish your work
before you go home.
We ought to help each other.
2、表“估计”They should get home by now. 表示“非常可能”的事，可译为“总应该”
If we start to work right now, we ought to finish it before lunch.(午饭前应当能干完)
