概  说

•       助动词(auxiliary)主要有两类：基本助动词(primary auxiliary)和情态助动词(modal auxiliary)。基本助动词有三个：do, have和be；情态助动词有十四个：

•       may, might; can, could; will, would; shall, should; must, need, dare, used to, ought to. have to

•       上述两类助动词的共同特征是，在协助主动词构成限定动词词组时，具有作用词的功能：

•       构成否定式：

•       He didn’t go and neither did she.

•       The meeting might not start until 5 o’clock.

•       构成疑问式或附加疑问式：

•       Must you leave right now?

•       You have been learning French for 5 years, haven’t you?

•       构成修辞倒装：

•       Nowhere can he obtain any information about his sister.

•       Hardly had he arrived when she started complaining.

•       代替限定动词词组：

•       A: Who can solve this crossword puzzle?

•       B: Tom can.

•       A: Shall I write to him?

•       B: Yes, do.

 

•      情态助动词的特征

•      基本助动词与情态助动词最主要的区别之一是，基本助动词本身没有词义，而情态助动词则有自己的词义，能表示说话人对有关动作或状态的看法，或表示主观设想：

•      What have you been doing since? （构成完成进行体，本身无词义）

•      I am afraid I must be going. （一定要）

•      You may have read some account of the matter. （或许已经）

•      除此之外，情态助动词还有如下词法和句法特征：

•      除ought和used以外，其他情态动词后面只能接不带to的不定式。如果我们把ought to和used to看做是固定词组的话，那么，所有情态动词无一例外地只能接不带to的不定式：

•      We used to grow beautiful roses.

•      I asked if he would come and repair my television set.

•             情态助动词在限定动词词组中总是位居第一：

•             They need not have been punished so severely.

•             情态助动词用于第三人称单数现在时的时候，没有词形变化，即其词尾无-s形式：

•             She dare not say what she thinks.

•             情态动词没有非限定形式，即没有不定式、-ing分词和-ed分词形式：

•             Still, she needn’t have run away.

•             情态助动词的“时”的形式并不是时间区别的主要标志。在不少场合，情态助动词的现在时和过去时形式都可以表示现在、过去或将来时间：

•             Would you mind very much if I ask you to do something?

•             She told him he ought not to have done it.

•             情态助动词之间是相互排斥的，即在一个限定动词词组中只能出现一个情态助动词，但有时却可以与have和be基本助动词连用：

•             You should have washed the wound.

•             Well, you shouldn’t be reading a novel.

 

情态助动词的意义和用法

 

•      情态助动词从最普通的意义上来说，是修饰分句意义的一种方式，它可以反映说话者对其表述是否真实和可能的程度作出判断。但不同的情态助动词本身所包含的意义和用法又不同，下面逐个分析。

•             一  can和could的用法

1    表示能力或客观可能性，还可以表示请求和允许。如：

•              Can you finish this work tonight?

•              Man cannot live without air.

•             2    Can I go now?   — Yes, you can.

•              注意：①could也可表示请求，预期委婉，主要用于疑问句，不可用于肯定句，答语应用can（即could不能用于现在时态的简略答语中）。如：

•                 Could I come to see you tomorrow?

•                 Yes, you can. （否定答语可用No, I’m afraid not.）

•                    ②can表示能力时，还可用be able to代替。如：

•                 I’ll not be able to come this afternoon.

3    表示惊异、怀疑、不相信的态度。（主要用在否定句、疑问句或惊叹句中）

•              Can this be true?

•              How can you be so careless!

•              This cannot be done by him.

4    “can (could) + have + 过去分词”的疑问或否定形式表示对过去发生的行为怀疑或不肯定。如：

•              He cannot have been to that town.

•              Can he have got the book?

•             二   may和might的用法

1   表示许可。

•             表示请求、允许时，might比many的语气更委婉一些，否定回答时要用mustn’t表示“不可以”、“禁止”、“阻止”之意。如：

•             You may drive the car.

•             Might I use your pen?   — No, you mustn’t.

•             2   用May I ... 征询对方许可在文体上比较正式，在口气上比较客气。在日常口语中，用Can I ... 征询对方意见在现代口语中更为常见。

 3  用于祈使句中表示祝愿，may 放在句首，表示祝愿 。如：

•             May you succeed!

4  表示推测、可能（疑问句不能用于此意）。

•             He may be very busy now.

•             四dare和need的用法

–          need表示“需要”或“必须”，作情态动词时，仅用于否定句或疑问句中，在肯定句中一般用must, have to, ought to,或should代替。如：

•             You needn’t come so early.

•             Need I finish the work today?

•             Yes, you must.

•             注意：needn’t + 不定式的完成式“表示本来不必做某事而实际上做了某事”。如：

•             You needn’t have waited for me.

–          Dare作情态动词时，主要用于疑问句、否定句和条件从句中，一般不用在肯定句中。如：

•             How dare you say I’m unfair.

•             He daren’t speak English before such a crowd, dare he?

–          Dare和need常用作实义动词，有时态、人称和数的变化，所不同的是，作实义动词时，在肯定句中，dare后面通常接带to的不定式，在否定和疑问句中，dare后面可接带to或不带to的不定式。如：

五  shall和should的用法

 

1  Shall用于第一人称，表示征求对方的意愿。如：

•             What shall we do this evening?

–          Shall用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。如：

•             Shall we begin our lesson?

•             When shall he be able to leave the hospital?

 3  Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。如：

•             You shall fail if you don’t work harder. （警告）

•             He shall have the book when I finish reading. （允诺）

•             He shall be punished. （威胁）

•             4   Should表示劝告、建议、命令，其同义词是ought to；在疑问句中，通常用should代替ought to。如：

•             You should go to class right away.

•             Should I open the window?

•             Should的含义较多，用法较活，现介绍三种其特殊用法。请看下面的句子：

•             I should think it would be better to try it again. 我倒是认为最好再试一试。

•             You are mistaken, I should say. 依我看，你是搞错了。

•             I should advise you not to do that. 我倒是劝你别这样做。

•              This is something I should have liked to ask you. 这是我本来想问你的。

•              从以上例句可以看出：情态动词should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。

•              Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能。相当于“万一”的意思。从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气。如：

•              Ask her to ring me up if you should see her. 你万一见到她，请让她给我打个电话。

•              If you should change your mind, please let us know. 万一你改变主意，请通知我们。

•              Should I (If I should) be free tomorrow I will come. 万一我明天有时间，我就来。

•              此外，Why(or How) + should结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会”。如：

•              Why should you be so late today? 你几天怎么来得这么晚？

•              — Where is Betty living? — 贝蒂住在哪里？

•              — How should I know? — 我怎么会知道呢？

•              I don’t know why you should think that I did it. 我真不知道你凭什么认为这件事是我干的。

•             六   will和would的用法

–           表示请求、建议等，would比will委婉客气。如：

•              Would you pass me the book?

–           表示意志、愿望和决心。如：

•              I will never do that again.

•              They asked if we would do that again.

–           用“will be”和“will (would) + have + 过去分词”的结构表示推测，主要用于第二、三人称。前者表示对目前情况的推测，后者表示对已经完成的动作或事态的推测。如：

•              This will be the book you want.

•              He will have arrived by now.

•              The guests would have arrived by that time.

•              I thought you would have finished this by now.

–           Would可表示过去反复发生的动作或某中倾向。Would表过去习惯时比used to正式，并没有“现已无此习惯”的含义。如：

•              The wound would not heal.

•              During the vacation he would visit me every week.

–           表料想或猜想。如：

•              It would be about ten when he left home.

•              What would she be doing there?

•              I thought he would have told you all about it.

 

•             七   ought to的用法

–          Ought to表示应该。如：

•             You ought to take care of him.

–          表示推测。注意与must表示推测时的区别：

•             He must be at home by now. （断定他已到家）

•             He ought to be home by now. （不十分肯定）

•             This is where the oil must be. （比较直率）

•             This is where the oil ought to be. （比较含蓄）

–          “ought to + have + 过去分词”表示过去应做某事而实际未做。如：

•             You ought to have asked him (but you didn’t).

•             这时，ought to和should可以互相换用。

•             注意：在美国英语中，ought to用于否定句和疑问句时，to可以省略。如：

•             Ought you smoke so much?

•             You oughtn’t smoke so much.

八 Had better 和Would rather

1    意为“最好”，后接不带to的不定式。如：

•              We had better go now.

•              Yes, we had (we’d better / we had better).

•              Hadn’t we better stop now? (Had we better not stop now?)

•              I think I’d better be going. （用于进行时态，表“最好立即”）

•              You had better have done that. （用于完成时态，表未完成动作）

•              注：①had best与had better同意，但较少用。②You had better … 用于同辈或小辈，对长辈不可用。

2     Would rather意为“宁愿”，表选择，后接不带to的不定式。如：

•              I’d rather not say anything.

•              Would you rather work on a farm?

•              Wouldn’t you rather stay here?

•              No, I would not. I’d rather go there.

•              由于would rather表选择，因而后可接than。如：

•              I would rather work on a farm than in a factory.

•              I would rather watch TV than go to see the film.

•              I would rather lose a dozen cherry trees than that you should tell me one lie.

•              I’d rather you didn’t talk about this to anyone. （句中的’d rather不是情态动词，would在此是表愿望的实义动词）

 

•             九  used to　的用法

–          Used to表示过去的习惯动作或状态，现在已不存在，在间接引语中，其形式可不变。如：

•             He told us he used to play football when he was young.

•             在疑问句、否定句、否定疑问句或强调句中，可有两种形式

•             疑问句 　　Did you use to go to the same school as your brother?

•             　Used you to go to the same school as your brother?

•             否定句 I usedn’t to go there.

•              I didn’t use to go there.

•             否定疑问句 Usen’t you to be interested in the theatre?

•             Didn’t you use to be interested in the theatre?

•             Usedn’t 亦可拼作usen’t，但发音皆为[ju:znt]。

 

•      强调句

•      I certainly used to smoke, but it was a long time ago.

•      I certainly did use to smoke, but it was a long time ago.

•      其反意疑问句或简略回答中，也有两种形式：

•      She used to be very fat, didn’t she? （正式）/ use(d)n’t she? （口语）

•      Did you use to play chess? Yes, I did.

•      Used you to get up early in the morning? Yes, I did. (Yes, I used to.)