情态助动词用法简述

dare, need

① dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。

eg. How dare you say such horrible words to me?

② need 作情态动词用时, 常用于疑问句、否定句，相当于肯定句中一般用must, have to, ought to, should。

eg. Need I finish the work today?

Yes, you must. / No, you needn't.

③ dare和 need作实义动词用时， 有人称、时态和数的变化，在肯定句中，dare后面常接带to的不定式，在疑问句和否定句中，dare后面可接带to或不带to的不定式，而need后面只能接带to的不定式。

eg. She doesn't dare (to)answer.

She needs to cook dinner for her sisters.

五. shall, should

① shall 用于第一人称，征求对方的意见。

eg. What shall I do ?

② shall 用于第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。

eg. You shall be punished,you bad boy!

六. will, would

① 表示请求、建议等，使用would使语气更加缓和。

eg. Would you give me a cup of coffee, please?

② 表示意志、愿望和决心。

eg. I will never do that again.

③ would表示过去反复发生的动作或某种倾向。

eg. During that summer, he would visit me every other day.

④ 表示估计和猜想。

eg. It would be about may when she come back to China.

七. should, ought to

① should表示“应该”，ought to表示义务或责任，语气更严重。

eg. I should help her because she is in trouble.

You ought to take care of her because she is your daughter.

② 表示劝告、建议和命令，should, ought to可通用，但在疑问句中常用should。

eg.Should I open the window?

③ 表示推测， should , ought to (客观推测), must(主观推测)。

eg. She must pass the exam. (断定)

She ought to/should pass the exam.(不太肯定)