情 态 动 词
情态动词有can/ could/ may/ might/ must/ have to/ shall/ should/ will/ would/ ought to/ need/ dare等。情态动词没有人称和数的变化，有词义，但不完整，不能独立作谓语，必须和不带to的动词不定式连用。
1、can与could
1can与could表示能力
eg: He can swim, but I can’t.
2can与could表示客观的可能性
eg: Kunming is called “Spring City”, but it can snow in winter.
3can与could表示请求时，使用could比can语气更委婉客气，此时could和can没有时间上的差别，它主要用于疑问句，不用于肯定句，因此回答时要改用can.
eg: ---Could I come here again tomorrow?
---Yes, you先进村 can./ No, I’m afraid not.
2、注意几组使用情态动词的提问和回答
eg: May I watch TV now?
---Yes, you may./ Yes, plea.
---No, you mustn’t./ No, you’d better not.
Must I do it at once?
---Yes, you must.
---No, you needn’t./ No, you don’t have to.
女朋友睡前故事Need I come?
---Yes, you must.
---No, you needn’t.
山药的作用3、can和may表示许可时，can侧重客观情况的“许可”，may侧重说话人主观上给予的“许可”。
eg: You can smoke now, as Grandmother isn’t here.苹果怎么恢复出厂
You may smoke here.
4、may用于祈使句中，表示祝愿
eg: May you succeed!
5、will的用法
1主语是人时，表示意愿
eg: I will never do it again.
2主语是物时，表示功能
eg: The watch won’t work./ The window won’t open.
6、shall的用法
怀古诗1与第一、第三人称连用的问句中，表示说话人征求对方的意见或 请求。
eg: What shall we do now?
Shall she come right now?
2与第二、第三人称连用的陈述句中，表示说话人给对方的命令、警告、允诺、或威胁等。
eg: You shall go with me. (命令)
Tell her that she shall have the book tomorrow. (允诺)
He shall be punished.( 警告、威胁)
3法律规定应用shall
eg: “The interest shall be divided into five parts, according to the agreement made by both sides. ”declared the judge.
另外，should也可以表示法律义务和规定
You are his father. You ought to get him to receive good education.
7、should的用法
1用于表示劝告或建议，作“应该”讲
开机启动项怎么设置eg: You should keep your promi.
2用于表示推测，作“可能”、“应该”讲
eg: They should arrive by two o’clock.
3用于第一人称时可表示说话人的一种谦逊、客气、委婉的语气
eg: I should advice you not to do that. 我倒是劝你别那样做。
4用于if引导的条件从句中，表示一件事听起来可能性很小，但也不是完全不可能，相当于“万一”，条件从句使用 “ (should) + V-原” 结构。
eg: Ask Tom to ring me up if you should e him.
If things should change suddenly, plea let me know.
5Why/ How + should结构表示说话人对某事不能理解，感到意外、惊异的意思：“竟会”
eg: Why should you be so late today? 你今天怎么来得这么晚？
I don’t know why you should think that I did it.
6should侧重表示主观上认为“应该”，ought to侧重表示客观上“按道理应该……”
eg: You should help them with their work.
“The interest shall be divided into five parts, according to the agreement made by both sides. ”declared the judge.
8、would与ud to
eg: He would get up early. 他过去常早起。（现在不知）
He ud to get up early. 他过去常早起。（现在已不）
ud to后可加静态动词表示状态，而would不行：
He ud to be a naughty boy.
ud to的反意疑问形式有两种：
She ud to go there, un’t she? / didn’t she?
9、could与was/were able to
was/were able to表示尖过去某一场合设法做成了某事，相当于managed to do, 含有“经过努力做到”的意思，而could则无此意义。
eg: The fire was big, but most people were able to escape from it.
10、need（需要）与dare（敢于）
都既可作情态动词又可作实义动词，作情态动词主要用于否定句及疑问句中（dare也可以用于条件句中）：
eg: You needn’t come so early.
Need I finish the work today?
How dare you say I’m unfair?
作实义动词, 有时态、人称和数的变化，不同的是：
need + to do
肯定句中：dare + to do 否定句及疑问句中：dare + (to) do
He is rich, so he needs no money.
Does she need to know it?
I dare to swim across the river.
He does not dare (to) answer.
11、情态动词表推测
送人东归
肯定句中一般用以下情态动词：must/ will/ would/ shall/ should/ can/ could/ ought to/ may/ might等；
否定句中一般用以下情态动词：can not/ could not/ may not/ might not等；
疑问句中一般用以下情态动词：can/ could
1对现在或将来的推测：V-情 + V-原/be动词
eg: It is already 12:00. You must be hungry.
---Are you coming to Jeff’s party?
---I’m not sure. I might go to the concert instead.
2对过去的推测：V-情 + have done/been
eg: The ground is wet. It must have rained last night.
You must have been out last night. I called you veral times, but nobody answered.
注意其反意疑问句的形式：
V-情 + have been 有时间状语 wasn’t/weren’t
done didn’t
没有时间状语hasn’t/haven’t
eg: They must have been very tired yesterday, weren’t they?
The children must have watered the flowers yesterday, didn’t they?
The minister must have arrived in Shanghai, hasn’t he?
12、非常有把握的肯定推测用：must
13、非常有把握的否定推测用：can’t
14、把握不大的肯定推测用：may/might
15、疑问句及感叹句中常使用：can
eg: Can this news be true?
How can you be so foolish?
How can it be that he was late for the opening ceremony.
东篱下
16、情态动词表示遗憾、责备和批评
should/ought to have done 本该做某事而实际上没做
shouldn’t/ought not to have done 本不该做某事而实际上做了
eg: You should come a little earlier.
You shouldn’t have left home without a word.
might/could have done 本来能够做某事而实际上没做
eg: ---I didn’t go to work yesterday becau my car broke down.
