1. 表示能力 (ability) “能够” Can you finish the work today? 2. 表示许可 (permission) “可以” You can go home now.
3. 表示请求 (request) “可否” Can I smoke here? 4. 表示推测语气 (否定句)
The story can’t be true.
He can’t have left, for his bike is here. （疑问句）
Can the story be true?
Who can have taken my dictionary? 5. can be 表示一时的情况或事实，理论上或习惯上的可能性： “会”
The road can be crowded during rush hours. SARS can be very dangerous. It could be cold here in March.
▲ may 和might
1. 表示许可 (permission) “可以” If I may say so, … You may go now.
2. 表示请求 (request) “可否” May I leave now?
---No, you can’t. Yes, please. 3. 表示推测语气 “可能”
He may be waiting for you now. He may have received the letter. I am not sure, but I may go there. 4. May sb. do…! 表示祝愿 May you succeed!
5. may well do sth 很有可能做某事 He may well not like the film. may/ might as well do sth 最好 He may as well change his attitude.
▲ will
1. 表示一般将来时
2. 表示意志、决心或意愿色彩 I will never do that again. I won’t tell you about that.
3. 表示习惯性动作
He will sit for hours doing nothing. 4. 表示倾向性，“总是，总会，会” Matches will not strike if they are damp. Man will die without water.
A lion will only attack a human being when it hungry.
▲ would
1. 表示过去将来
He told me that he would come the next week. 2. 表示过去的习惯性动作
He would sit for hours doing nothing. 3. 表示客气的请求或邀请（疑问句） Would you like to join us in the game? Would you be kind enough to help me?
▲ shall 1. 在一、三人称的疑问句中，表示征求对方意见。 Shall I open the door? Shall he come in?
When shall we meet again?
i2. 在二、三人称的陈述句中，表示说 者给对方的命令、警告、允诺、决心 威胁等。
You shall have the book when I finish reading it. You shall fail if you don’t work hard. Nothing shall stop us leaving now.(决心) He shall not enter my house again.（命令）
3. 在法律、条文、规章等文件中，用shall表示
义务、规定。
Each citizen shall carry his ID card when
traveling.
The interest shall be divided into five parts
according to the agreement.
▲ should
1. 表示义务或责任
I should go to his help because he is in trouble. I should pay Mary a visit. 2. 表示建议或劝告
You should go to class right now.
3. 表示（将来）合理的推测或明显的结果。 It’s 3 o’clock now. The football match should
begin soon. She should be at home. 4. 表示虚拟语气
You should have come earlier. You shouldn’t have done that. 5. 表示惊讶 “竟会，竟然”
It is a pity that you should be so careless.
It is strange/surprising that you should speak to him like that.
6．表示不确定 “万一”
If I should see him, I will tell him about it.
Should you be late, you might inform me in advance.
▲ must
1. 表示义务或强烈的劝告 “必须，一定要” You must come in time.
否定：needn’t \\ don’t have to “没必要” 2. 表示推测语气（肯定句） “一定，肯定” 否定can’t/couldn’t
He must be in the library now.
He must be doing his homework now. He must have left for home.
3. 表示不耐烦或不愉快的事 “非要，偏要” Why must it always rain on Saturday? ---Who is the girl standing over there?
---Well, if you ___ know, her name is Mabel.(04 天津)
A. may B. can C. must D. shall
Just as I sat down to supper, the telephone must ring.
4. mustn’t 表示“禁止，不许” You mustn’t park your car here.
▲ 推测语气
must have done 肯定已经做了某事
may \\ might have done 可能已经做了某事 can’t \\ couldn’t have done不可能做了某事
▲ 虚拟语气
should have done 本来应该做而未做 shouldn’t have done本来不应该做而做了 might have done 本来有可能做某事 could have done本来能够做某事
needn’t have done 本来没有必要做某事但做了
因篇幅问题不能全部显示，请点此查看更多更全内容