情态动词
can , could , may , might , must , shall , will , would , need , dare , dared , should , ought to , used to; had better; would rather
情态动词表猜测
1) should / ought to 照说应该，估计 The photo should be ready by 12 o’clock .
2) may / might / must / can’t / couldn’t 表猜测，
a.非常肯定的猜测
must “肯定, 一定” can’t “肯定不,不可能”He must be at home now.
He must like English. He can’t be at home now.
He can’t have much money.
注意: mustn’t “不准,禁止”You mustn’t talk in class.
b.表示不太肯定的猜测： may/might 可能 may not, might not 可能不
can/could 只用于疑问句和否定句中
You may not remember me. I thought he might remember me.
---Can it be true.? --- No, it can’t true.
could/might 表示过去，但也可表示现在，表示现在时，它的可能性比can/ may要小。
He may/might be in Class One .
注意1：表猜测时，时态体现在情态动词后面
a.对过去的猜测-情态动词后面用完成时
1 He must have read books about Shakespeare because he knows so much about him.
2 -- I called him last night, but nobody answered.
--He can’t /couldn’t have been at home.
3 In those days I may have been pretty.
b.对现在的猜测 ---情态动词后面用动词原形或进行式。
1 He can’t like this kind of book.
2 They may be playing football now.
注意2 :a。may / might / must / can’t / couldn’t 表猜测时的反意疑问句。
He might have a lot of work to do now , doesn’t he ?
He may have missed the early bus , hasn’t he ?
I must have been asleep when you rang me , wasn’t I ?
It can’t rain tomorrow , will it ?
He must be studying in the classroom now , isn’t he ?
b．can 表猜测一般用于否定句或疑问句中，在肯定句中往往表示“一时的可能性”
“有时可能会”
Training by yourself can be highly dangerous .
二）情态动词表虚拟
could have done 本可以-----
may/might have done 本来可能---
should / ought to have done 本来应该---- shouldn’t/ought not to have done本不该---
needn’t have done 本不必----
wouldn’t have done 本不会---
1 Chuck also learns that he should have cared more about his friends .
2 You needn’t have come here so early.
3.You needn’t have gone there yesterday .
4.We ought to have given you more help , but we were so busy .
5.We could have walked to the station , it was so near .
****三）几组词的区别
1）can , be able to a.. can 只有现在式和过去式，而be able to 有各种时态，
b. can 表能力，be able to 表成功地完成某一具体动作，相当于manage to do ,succeed in doing
Below the 11th floor people were able to escape .
2) must , have to have to “必须，不得不”表客观需要
must 表说话人的主观看法
3）would , used to 两者都可以表示过去的习惯。但would表示过去反复发生的动作或过
去的一种倾向，现在可能还存在，而used to表示现在不复存在的过去的状态、情况和动
作。
Often he would hear a long low whistle and the sound of a metallic noise .
I used to have an old jeep .
** 注意的否定和疑问句，
Used you to go to the same school ? = Did you use to go to the same school ?
I usedn’t to smoke . = I didn’t use to smoke .
4) need , dare 作为情态动词，一般用于否定句，疑问句，条件句中(除 I dare say ----)，
没有人称和数的变化，否定句在其后加not ，疑问句把need , dare ,dared 提前，后面接
动词原形。***除了在I dare say---这种习惯用语中
---If you die ,who will get your money?----I dare say my uncle will.
而作为及物动词时，有人称、数和时态的变化，否定句，疑问句要借助于助动词do ,
does ,did 。跟不定式作宾语。
She dare not say what she thinks . = She doesn’t dare to say what she thinks .
You don’t need to read the book if you don’t want to.
5)will 1）表示说话时做出某种决定时. ---- The phone is ringing . ----- I’ll answer it .
2) 表示一种倾向、习惯性动作或说话人的揣测的意见。
Without water flowers will die . After supper, he will have tea.
6).shall 1）用于第一人称，表示将来，
2）用于第一、三人称，在问句中表示征求别人的意见或向对方请示
-----Shall he wait outside or come in ?
3）用于第二、三人称，表示说话人对对方的命令、警告、允诺、威胁、决心。
He shall have the book when I finish reading .