五、非谓语动词(Non-finite Verb)
在英语中，不是用于句子谓语而是用于担任其他语法功能的动词叫做非谓语动词，也称作动词的非限定形式。
非谓语动词有三种形式：不定式(the Infinitive)、分词(the Participle)和动名词(the Gerund)。
不定式
1. 构成与形式
不定式由不定式符号“to + 动词原形”构成(有时不带to)。前面可以加某些疑问代词，如what, who, which, 或疑问副词，如when, where, why等，构成特殊的不定式短语，如what to do next, how to get there等。
不定式形式有：
主动形式 | 被动形式 | |
一般式 | to do | to be done |
完成式 | to have done | to have been done |
进行式 | to be doing | to be being done |
完成进行式 | to have been doing |
2. 用法
不定式不能单独作谓语，没有人称和数的变化，具有名词、形容词和副词的特征，而且还保留着动词的特征，因而可以有状语修饰，如果是及物动词，还可以带宾语，从而构成不定式短语。不定式或不定式短语在句子中可以作主语、表语、宾语、定语、状语、主语补足语和宾语补足语。
1)作主语
To make a plan for our future is important.
How to get enough capital is still a question.
It is difficult to make a decision without knowing all the facts.
2)作表语
The important thing is to save lives.
What he wanted to do was to wash his hands of it.
3) 作宾语
I like to go for a walk in the warm sunshine.
We must remember to follow the safety rule.
4)作定语
She usually has a lot of meetings to attend in the evenings.
He was always the first to come and the last to leave.
There are some things to be grateful for.
5) 作状语
She decided to work harder in order to catch up with the others.
He lifted a rock only to drop it on his own feet.
6) 作主语补足语
It is reported to be true.
The education of the young is seen to be of primary importance.
7) 作宾语补足语
Please remind me to take my medicine tomorrow.
They didn’t allow her to park the car in this street.
有一些动词后用作宾语补足语的不定式通常不带to。这种动词有两类：一类是感官动词，如feel, see, hear, watch, notice等;另一类是使役动词，如make, let, have等，如：
Did you notice him leave the house?
The made the boy go to bed early.
3. 时态与语态
1)完成式
I am sorry to have kept you waiting.
To have known her is an honor.
2) 进行式
They seem to be getting along quite well.
He pretended to be listening attentively.
3) 完成进行式
The famous singer is said to have been collecting folk songs in Xinjiang.
John is said to have been studying for a shole morning.
4) 被动式
I wish to be excused.
he was very pleased to have been given such an opportunity.
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