助动词 & 情态动词

简介

助动词（Auxiliary Verb）和 情态动词（Modal Verb）是辅助 实义动词 构成谓语的动词。

二者 本身不能单独作谓语，必须与实义动词配合使用。

助动词

助动词 用于构造 时态、语态、疑问句、否定句 和 强调。

基本助动词

助动词	作用	示例
be	构造进行时态、被动语态	She is reading.
have	构造完成时态	He has finished.
do	构造一般现在时态、一般过去时态的疑问句、否定句、强调	Do you know? / I do know.
will	构造一般将来时态、表示意愿	I will go.
shall	构造一般将来时态（第一人称，正式）	We shall see.
would	构造过去将来、表示委婉、表示假设	I would like some tea.
should	构造过去将来、表示建议或义务	You should rest.

助动词的语法功能

构造时态

• be doing：进行时态
• have done：完成时态
• have been doing：完成进行时态
• will do：将来时态

Example

• She is writing a letter.
• He has finished his homework.
• I will call you tomorrow.

构造语态

be done 构造被动语态（详见 被动）。

Example

• The book was written by him.

构造疑问句和否定句

一般现在时态、一般过去时态的疑问句和否定句通过 do/does/did 构造。

Example

• Do you like music?
• I do not like music.
• Did he go?
• He did not go.

强调

在肯定句中，do/does/did 可置于实义动词前表示强调。

Example

• I do love you.
• She does know the answer.
• He did come yesterday.

情态动词

情态动词（Modal Verb）表示说话人的 语气、态度 或 可能性，本身不表示具体动作。

形态特征

情态动词具有以下 共同特征：

1. 无人称和数的变化（不加 -s）。
2. 后接 动词原形（不带 to，ought to 例外）。
3. 自身构造疑问句和否定句，无需 do。
4. 没有非谓语形式（无 -ing, -ed 等形式）。

Example

• He can swim. He cans swim.
• Can you help me? Do you can help me?
• I cannot do it. I do not can do it.

常见情态动词

情态动词	核心语义	示例
can	能力、许可、可能（现在）	I can swim.
could	can 的过去式、委婉请求、虚拟推测	Could you help me?
may	许可、可能（现在）	You may leave now.
might	may 的过去式、不确定推测	He might be at home.
must	必须、强烈推断（一定）	You must follow the rules.
have to	客观必要（外在原因）	I have to leave early.
shall	第一人称将来、征询意见、命令义务	Shall we dance?
should	建议、义务、可能性推断	You should see a doctor.
will	意愿、习惯、推测	He will help us.
would	礼貌请求、过去习惯、虚拟	Would you mind?
ought to	道义上应当	You ought to respect them.
need	需要（疑问句、否定句中作情态动词）	You needn't worry.
dare	敢（疑问句、否定句中作情态动词）	He dare not speak.
used to	过去常常（现在已不）	I used to smoke.

推断语气强度

按 推断确定性 由弱到强排序：

$$\text{might} < \text{may} < \text{could} < \text{can} < \text{should} < \text{ought to} < \text{will} < \text{would} < \text{must}$$

Example

• He might be at home.（也许在家，可能性低）
• He may be at home.（可能在家）
• He must be at home.（一定在家）

情态动词 + 完成式

情态动词 + have done 表示对 过去 的推测或评价。

结构	语义	示例
must have done	肯定的过去推测（一定做过）	He must have left.
may/might have done	不确定的过去推测（可能做过）	She may have forgotten.
can't/couldn't have done	否定的过去推测（不可能做过）	He can't have stolen it.
should have done	过去应该做但没做（带责备）	You should have called me.
ought to have done	同上，更正式	You ought to have studied harder.
needn't have done	过去做了但没必要	You needn't have brought an umbrella.
would have done	虚拟过去（详见 动词语气）	I would have helped you.

区分

must vs. have to

• must：主观必要，来自说话人意愿。
• have to：客观必要，来自外部条件。

Example

• I must finish this. (自己想完成)
• I have to finish this. (被要求完成)

tip

• must 没有过去式，过去时态用 had to。
• must not（禁止）和 don't have to（不必）含义不同。

should vs. ought to

二者均表 应当，ought to 更正式、道义色彩更强，should 更日常。

shall 的使用

shall 在现代英语中使用减少，仅在以下场景常见：

• 第一人称征询意见：Shall I open the window?
• 法律条文中的 应当：The seller shall deliver the goods.

will 的多重含义

• 将来时态助动词：I will leave tomorrow.
• 表意愿：I will help you.
• 表习惯：He will sit there for hours.
• 表推测：That will be the postman.

思维导图