情態(tài)動(dòng)詞概述
特征
1)情態(tài)動(dòng)詞(modal verb)本身有詞義，表示說(shuō)話人的語(yǔ)氣或情態(tài)，但詞義不完全，不能單獨(dú)用作謂語(yǔ)動(dòng)詞，一般只能和動(dòng)詞原形一起構(gòu)成謂語(yǔ)動(dòng)詞。
2)情態(tài)動(dòng)詞所表示的情態(tài)有：命令、允諾、請(qǐng)求、拒絕、愿望、愿意、義務(wù)、必要、可能、能力、敢于、需要等。
3)情態(tài)動(dòng)詞(ought除外)和助動(dòng)詞shall，will，should，would一樣，后面的動(dòng)詞不定式一般皆不帶。
形式變化
1)沒(méi)有人稱和數(shù)的變化，第三人稱單數(shù)的現(xiàn)在時(shí)也無(wú)變化。如：
I can We can
You can You can
He
They can
She can
It
2)有些情態(tài)動(dòng)詞有過(guò)去式，有少數(shù)過(guò)去式和它的原形相同。
a)有過(guò)去式的情態(tài)動(dòng)詞有：
may -- would
can ―― could
may―― night
shall -- should
have to -- had to
b)過(guò)去式不變的情態(tài)動(dòng)詞有：
must - must (或had to)
ought to - ought to
need---need
dare - dare(亦可用dared)
3)大多數(shù)情態(tài)動(dòng)詞后面可用動(dòng)詞的進(jìn)行式、完成式和被動(dòng)形式，如：can(may，must)be doing，can(may，must) have done，can(may，must)be done等。
否定式
情態(tài)動(dòng)詞和助動(dòng)詞一樣，后面可直接跟否定詞not?，F(xiàn)將情態(tài)動(dòng)詞的否定式及其否定式的簡(jiǎn)略式(簡(jiǎn)略式用于口語(yǔ)中)列舉如下：
shall not--shan't [FB:nt]
will not---won't [wEunt]
can not-can't [kB:nt]
must not-mustn't [5mQsnt]
should not-- shouldn't
would not-- wouldn't
could not-- couldn't
dare not- daren't [dZEnt]
need not-- needn't
在疑問(wèn)句中的用法
情態(tài)動(dòng)詞在疑問(wèn)句中的用法和助動(dòng)詞相同。如：
May I ask you a question? 我可以問(wèn)你一個(gè)問(wèn)題嗎?
Can you let me use your dictionary for a minute? 你能把字典借我用一會(huì)兒?jiǎn)?
Would you like to visit the heavy machinery plant? 你想?yún)⒂^重型機(jī)器廠嗎?
注意have to在疑問(wèn)句中的位置。如：
Do you have to go out today? 你今天一定得出去嗎?
Does he have to finish the work tomorrow? 他明天非做完這項(xiàng)工作不可嗎?