英文文法情態動詞：Would、Could、Might、May、Should等分別與正確用法

本周文章要討論的主題為情態動詞的使用規則，以及如何在不同情境之下運用這類動詞。

 

情態動詞是一種用來表達情態的助動詞，因此又名為情態助動詞

 

具體來說，情態動詞是用來表示可能性、能力、意願、義務的一種動詞，其最主要目的為說明後方承接的主要動詞具有什麼樣的功能，和一般動詞的使用有許多不同之處，例句如下：

 

1. 情態動詞的第三人稱不加s。

 

例句：

 

He can speak Chinese.

She should be here by 9:00.

 

2. 無論是現在簡單式或是過去簡單式，皆使用not來表達否定語氣。

 

例句：

 

He should not be late.

They might not come to the party.

 

3. 情態動詞不能以過去式或未來式的形式表達。

 

錯誤：He will can go with us.

錯誤：She musted study very hard.

 

關於情態動詞的使用

 

情態動詞表達的情態類型如下：

 

1. 可能性
2. 能力
3. 義務
4. 建議
5. 許可
6. 習慣

 

所有情態動詞的種類如下：

 

Can, could, may, might, will, would, must, shall, should, ought to

 

切記：情態動詞的後方會承接不定詞，但一般不使用to

 

例句：

 

You must stop when the traffic lights turn red.

You should see the doctor.

There are a lot of tomatoes in the fridge. You need not buy any.

 

例外：

 

You ought to go to the doctor.

 

1. 可能性

 

首先，情態動詞可用於表達某件事情在過去／現在／未來發生的確定程度。

 

例句：

 

It’s snowing, so it must be very cold outside.

I don’t know where John is. He could have missed the train.

This bill can’t be right. £200 for two cups of coffee!

 

2. 能力

 

談到技術或能力時，會使用can或could。

 

例句：

 

She can speak six languages.

My grandfather could play golf very well.

I can’t drive.

 

3. 義務與建議

 

若要表達某件事情有無必要，或是給予建議，可使用must或should一類的情態動詞。

 

例句：

 

Children must do their homework.

We haveto wear a uniform at work.

You should stop smoking.

 

4. 許可

 

若要徵詢或給予同意，可使用can、could、may一類的情態動詞。此外，情態動詞也可以用來表達「禁止做某件事」的概念。

 

例句：

 

Could I leave early today, please?

You may not use the car tonight.

Can we swim in the lake?

 

5. 習慣

 

若談到平常或過去的習慣或行事做法，可使用will或would來表達。

 

例句：

 

When I lived in Italy, we would often eat in the restaurant next to my flat.

John will always be late!

 

情態動詞一覽表：

情態動詞	解釋	表達的情態類型	例句
must	to have to	100% obligation	I must stop when the traffic lights turn red.
	to be very probable	logical conclusion (deduction)	He must be very tired after such enormous work.
must not	not to be allowed to	prohibition	You must not smoke in the hospital.
can	to be able to	ability	I can swim.
	to be allowed to	permission	Can I use your phone please?
	it is possible	possibility	Smoking can cause cancer!
could	to be able to	ability in the past	When I was younger I could stay up all night and not get tired.
	to be allowed to	more polite permission	Excuse me, could I just say something?
	it is possible	possibility	It could rain tomorrow!
may	to be allowed to	permission	May I use your phone please?
	it is possible, probable	possibility, probability	It may rain tomorrow!
might	to be allowed to	more polite permission	Might I use your phone please?
	it is possible, probable	weak possibility, probability	I might come and visit you in America next year, if I can save enough money.
need	necessary	necessity	Need I say more?
need not	not necessary	lack of necessity/absence of obligation	I need not buy any tomatoes. There are plenty in the fridge.
should/ought to	used to say or ask what is the correct or best thing to do	50% obligation	I should/ought to see a doctor. I have a terrible headache.
	to suggest an action or to show that it is necessary	advice	You should / ought to revise your lessons.
	to be very probable	logical conclusion (deduction)	He should / ought to be very tired after such enormous work.
had better	to suggest an action or to show that it is necessary	advice	You’d better revise your lessons.

 

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