结构： 情态动词 + 动词原形

can/could

can/could 表示能力

1. 用 be able to 代替 can (现在)/could (过去) 的能力：能怎么样
2. 客观可能性（can 的可能性大）：可能怎么样
3. 表示请求和允许：可以怎么怎样

• He can/could/is able to swim. // 他会游泳。

• He can/could come tomorrow. // 他可以明天来。

• Can/Could I stay here? // 我可以住在这里吗？Could 比较委婉

may/might

may/might 表示可能性，may 的可能性大，请求、允许，might 更委婉

口语中常用的回答

• Yes, please.
• No, you can't/mustn't (禁止，不准).

• He may/might come here by bus.
• May/Might I join you?
  • Yes, please. / No, you can't /No, you mustn't.

练习

She (could) speak French before, but now she (can't). // 过去用cloud  现在用can

(Might) I come in? // might may could can都可，委婉程度依次递减
Yes,please.

must/have to

must/have to 表示必须、必要。must 表示主观多一些，have to 表示客观多一些。

have to 有时态和数量的变化

must 和 have to 二者的否定含义不大相同：

You mustn't go.你不准走。
You don't have to go. 你不必走。

• You must get up early. // 你必须早起。 主观要求
• It's going to rain, I have to go home now. // 天要下雨了，我得回家了。 客观要求

should/ought to

should 表示劝告、建议、命令，其同义词是 ought to ；should 强调主观看法，而 ought to 强调客观要求。在疑问句中，通常用 should 代替 ought to。

• You should/ought to do the job right now. // 你应该马上做这项工作。
• Should they stay here now? // 他们现在应该留在这里吗？

练习

I (must) go and see my mother in hospital tomorrow.    // must/have to均可，如果上文提及其他人已经去了，客观上我也必须去了则使用have to
  (必须)

You (should) work harder than that.	// should/ought to均可
	(应该)

need/don't have

need ：需要

1. 情态动词
2. 实义动词，有第三人称单数和时态的变化，后面可加动词不定式 to 动词原形 。

基本结构：

情态动词：need + 动词原形
实义动词：need to + 动词原形

情态动词

• He need come here early.
• He needn't come here early.
• Need he come here early? // 一般疑问
  • Yes, he need. / No, he needn't.

实义动词

• He needs to come here early.
• He doesn't need to come here early. // 否定的助动词，取决于时态
• Does he need to come here early? // 疑问句，助动词前置
  • Yes, he does. / No, he doesn't.

---

回答 must 和 have to 的提问句时，否定式使用 needn't , don't have to 等回答方式.

笔记

在使用 don't have to 时需要考虑人称、时态变化。

• Must I come here early tomorrow? // 我明天必须早点来吗？
  • No, you needn't. / No, you don't have to. // 这里不能用 mustn't (不准)

练习

You (needn't) do it again.   // don't have to也可
你不需要重复做了。

He (needn't) worry about it.	// doesn't have to也可
这件事他无需担心。

(Does) he need to do homework f irst?  // need后有不定式to，因此是实义动词，需要使用一般现在时的助动词单三does
他需要先做作业吗？

had better

had better 表示 “最好做某事”，had 虽然是过去式，但不表征过去，better 后面接动词原形

基本形式： had better + 动词原形

• He had better eat more.
• You'd better finish it right now.

否定形式： had better not + 动词原形

• He had better not eat more.

would rather

would rather 表示 “宁愿、宁可、最好、还是…… 为好”，语感上比 had better 要轻。

基本形式： would rather + 动词原形

• You would rather deal with it now.

否定形式： had better not + 动词原形

• You would rather not deal with is now.

练习

You (had better) stay here.
你最好待在这儿。

I (would)(rather) not say it.
我还是不说的好。

used to/would

used to 、 would 表示过去习惯性动作，可翻译为 “过去常常……”

基本形式：

used to + 动词原形
would + 动词原形

1. used to 可指过去的状态或情况， would 则不能

• The novel used to be popular. // 这本小说过去很受欢迎。

2. would 表示反复发生的动作。如果某一动作没有反复性，就不能用 would，只能用 used to

• He would practise English every week. // 他每周都练习英语。 every week 说明是反复发生的动作
• I used to live in Beijing. // 我过去住在北京。 住在北京是过去的状态或情况，而不是反复发生动作

3. used to 表示过去经常性或习惯性的动作或状态现在已经结束， would 则表示有可能再发生。

• People used to believe that the earth was flat. // 过去人们认为地球是平的。 现在没人会认为是平的
• He would go to the park as soon as he was free. // 他一有空就去公园。 去公园发生在过去，以后也可能会去

练习

The window (used to) be open.	// 过去已经打开了

They (would) gather together every week. // every week 反复发生，used to也可，但表达的含义是现在不再聚会了。
// would：他们每周聚会一次。	used to：他们过去每周都聚会。

Sam (used to) paly golf, but he doesn't now.  // but he doesn't now可知现在不去了

否定

基本形式： 情态动词 + not + v（动词）原形

• He can't sing an English song.
• He may not know her.
• He mustn't go there.
• He doesn't have to go there. // 特殊

疑问

基本形式： 情态动词 + 主语 + v原形

• Can he sing an English song?
  • Yes, he can. / No, he can't.
• Must he go there?
  • Yes, he must. / No, he needn't.
• Does he have to go there? // 特殊
  • Yes, he does. / No, he doesn't.

练习

(Can) I stay here?
Yes, please.

(Must) she go back now? 
No,she needn't.

(Does) he have to get up at 9:00?   // 居中使用了have to，显然是要填助动词
Yes,he does.

情态动词 + have + p.p.

1. 表达过去事实
2. 推测的含义（但助动词 should 例外），译为可能已经……、准是已经……。

• He can/could have arrived. // 他可能已经到了。
• He may/might have arrived. // 他可能已经到了
• He must have arrived. // 他一定到了。

表达他到了的可能性程度由高到低依次为：must、can、could、may、might

---

should have p.p. ：本应该……

needn't have p.p. ：本不需要……

• He should have arrived. // 他本应该已经到了
• They should have finished the work. // 他们本应该完成这项工作的
• You needn't have done so. // 你本不需要这样做的

---

must have p.p. ：准是已经……

can't have p.p. ：不可能已经……，must 的否定形式

• He must have arrived. // 他一定（准是已经）到了
• He can't have arrived. // 他不可能已经到了

::: detail 练习

He (can) have arrived.	// must、can、could、may、might
	(可能)
	
He (must) have arrived.   // 最有可能
	(准是)

You (needn't) have done so.
	(本不需要)

They (should) have finished the work.
	(本应该)
	
He (can't) have arrived.
	(不可能)

:::