不定式

动词不定式
一、构成与特点：
基本形式为to+动词原形。

动词不定式没有人称和数的变化，在句中不可作谓语。

在句中可以作主语、表语、宾语、定语、宾语补足语和状语。

1、一般式：动词不定式的一般式所表示的动作或状态，与句中谓语动词表示的动作或装态是同时发生的，或在之后发生的。

如：
He seemed to be tired. She stopped to have a cup of tea.
2、进行式：表示在谓语动词的动作或状态发生时正在进行的动作。

如：
He pretended to be waiting for someone.
3、完成式：表示发生在谓语动词之前的动作。

如：He seems to have been ill.
二、用法：
1、作主语：To study hard is important. To give is better than to receive.
作主语时常用it作形式主语，构成“It is + 形容词+不定式”句型。

如：
It is important to study hard. It is better to give than to receive.
2、作宾语：I hope to see her soon.
3、作表语：The important thing is to save lives.
4、作宾语补足语：I asked him to give me the book on the desk.
5、作定语（必须后置）：
1）、当名词有序数词、最高级或next等修饰时：This is the fittest food for you to eat.
2）、说明名词的用途：I need some paper to write a letter on.
3）、在promise, wish, hope, ability, determination, resolution等名词后面时；
4）、用于have(there be, here is) something to do 结构中；
5）、用于It’ s time(high time, the best time) to do 结构中；
6、作状语：可以表示原因、目的、结果等。

如：He was surprised to hear the news.
三、不定式的否定式：
不定式的否定形式为not to + 动词原形，有时也可用never to + 动词原形。

如：
I asked him not to throw paper on the ground. He promised never to tell a lie.
四、不定式的被动语态：
不定式的被动语态有两种：1、一般式：to be done；2、完成式：to have been done。

It is necessary for her to be invited to the meeting. To be understood by others is a good thing.
I wish to be given more time. She is glad to have been given such a good chance.
【注意】
1、easy，difficult等形容词后面的不定式常用主动式代替被动式。

如：
The song is easy to learn. 不说to be learned. The book is difficult to read.
2、there be句型中不定式修饰主语时，用主动式或被动式均可，但在正式文体中要用被动式，如：There are a lot of thing to do/be done today.
但是，如果不定式带有for引起的逻辑主语，指明了不定式动作的执行者，则只能用主动式。

3、有时，不定式的主动式和被动式的意义不同，如：
She has some clothes to wash. She has some clothes to be washed.。