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高中情态动词精讲与解析

来源:英语阅读 编辑:英语学习 时间:2017-04-10

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;情态助动词有十三个:may, might; can, could; will, would; shall, should; must, need, dare, used to, ought 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:
1) 构成否定式:
He didn't go and neither did she.
The meeting might not start until 5 o'clock.
2) 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?
3) 构成修辞倒装:
Nowhere can he obtain any information about his sister.
Hardly had he arrived when she started complaining.
4) 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:
1) 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.
2) 情态助动词在限定动词词组总总是位居第一:
They need not have been punished so severely.
3) 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.
4) 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.
5) 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.
6) 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.

现将情态助动词的各种形式列表如下:

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。

1) 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.
— 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.
2. 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.
3. “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?

2) 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.
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。

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