情態(tài)動(dòng)詞的語(yǔ)法特征
情態(tài)動(dòng)詞表示說(shuō)話人對(duì)動(dòng)作或狀態(tài)的各種觀點(diǎn)和態(tài)度，如需要、猜測(cè)、意愿或懷疑等。情態(tài)動(dòng)詞有詞義，但不完全，是所謂的“輔助性”動(dòng)詞，在句中不能單獨(dú)充當(dāng)謂語(yǔ)。
A.情態(tài)動(dòng)詞的各種形式見(jiàn)下表：
情態(tài)動(dòng)詞
may
might
can
could
must
have to
ought to
will
would
shall
should
need
dare
used to
否定式
may not
might not
cannotcan not
could not
must not
do not have to
ought not to
will not
would not
shall not
should not
need not
dare not
used not to
did not use to
簡(jiǎn)略否定式
mayn't(老式英語(yǔ)，現(xiàn)在不常見(jiàn))
mightn't
can't
couldn't
mustn't
don't have to
oughtn't to(否定句中to可省略)
won't
wouldn't
shan't(只用于英國(guó)英語(yǔ))
shouldn't
needn't
daren't
usedn't to
didn't use to
B.情態(tài)動(dòng)詞除ought to, used to等外，后面只接不帶to的不定式。
1.情態(tài)動(dòng)詞+do
You shouldn't be so careless.你不該這樣粗心大意。
Jessica told him yesterday she might not go on the trip.
杰西卡昨天告訴他，她可能不去旅行了。
Difficulties can and must be overcome.
困難能夠而且必須克服。
2.情態(tài)動(dòng)詞+be doing
She must be listening to pop music.
她肯定在聽(tīng)流行音樂(lè)。
You should be reviewing your lessons.
你應(yīng)該在復(fù)習(xí)功課。
My mother maymight be cooking now.
我媽媽可能正在做飯。
3.情態(tài)動(dòng)詞+have done
They might have visited the Great Wall.
他們可能參觀過(guò)長(zhǎng)城了。
He must have got up very early to catch the train.
他一定起得很早去趕火車了。
You ought to have come earlier.
你本該早一點(diǎn)兒來(lái)。
4.情態(tài)動(dòng)詞+be done
This word can also be used as a verb.
這個(gè)詞也可以用作動(dòng)詞。
Something must be done to stop pollution.
必須采取措施來(lái)制止污染。
The work ought to have been finished long ago.
這工作早就該完成了。
C.情態(tài)動(dòng)詞第三人稱單數(shù)一般現(xiàn)在時(shí)沒(méi)有詞形變化。
You ought to wear a raincoat.
你應(yīng)該穿件雨衣。
She ought to wear a raincoat.
她應(yīng)該穿件雨衣。
Plants must have oxygen in order to live.
為了存活植物必須有氧氣。
A plant must have oxygen in order to live.
為了存活植物必須有氧氣。
D.情態(tài)動(dòng)詞的時(shí)態(tài)并不是區(qū)分時(shí)間的主要標(biāo)志。在一些場(chǎng)合中，情態(tài)動(dòng)詞的現(xiàn)在式和過(guò)去式都可以表示現(xiàn)在時(shí)間、過(guò)去時(shí)間或?qū)?lái)時(shí)間。
I'm afraid it might rain tonight.
我看今晚可能要下雨。
Could I borrow your thermos
我可以借用你的暖水瓶嗎?
It's a nice day today. We could go for a walk.
今天天氣不錯(cuò)，我們可以出去散散步。
E.情態(tài)動(dòng)詞是互相排斥的，一般不允許兩個(gè)意義相近的情態(tài)動(dòng)詞連用。
【誤】Soldiers must have to obey orders.
【正】Soldiers have to obey orders.
軍人必須服從命令。
【正】Soldiers must obey orders.
軍人必須服從命令。
【誤】Can I be able to borrow two books at a time
【正】Can I borrow two books at a time
我能一次借兩本書(shū)嗎?
【正】Will I be able to borrow two books at a time
我能一次借兩本書(shū)嗎?
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