1、不定式的形式

以动词do为例

1.不定式的主动语态与被动语态

一 般式to do (主动，未发生) to be done (被动， 未发生)

完成式to have done (主动，已完成)

to have been done (被动，已完成)

进行式to be doing (主动，正在进行)

完成进行式to have been doing (主动， 完成进行)

2、不定 式的句法功能

(1)不定式作主语

To hear from you is good. 收到你的来信很好

To be a good student is not easy. 做一个好学生不容易

不定式作主语时，为了保持句子的平衡，往往以it作形式主语，不定式作为真正主语置于谓语动词后。如:

It‘ s good to hear from you.

It’s not easy to be a good student.

(2) 不定式作宾语

通常用于want, hope, wish, like, need, hate, begin, start,remember, agree, learn, refuse, manage, help 等词后。如:

①forgot to close the door.

我忘记关门了

②Please remember to write to me.

请记得给我写信

(3)不定 式作表语

①My job is to pick up litters.

我的工作是捡起那些乱丢的垃圾

②He seemed to have heard something.

他看起来似乎听说了些事

(4) 不定式作定语

不定式作定语时，须放在它所修饰的名词或代词后。如:

①l have a lot of letters to write.

我有很多信要写

②have a lot of homework to do.

我有很多作业要做

(5) 不定式作宾补

通常用于want, wish, ask, order, tell, know, help, advise,allow, cause, force 等词后。如:

①He ordered her to leave right away.

他命令她马 上离开

②He was forced to follow his order.

他被强迫遵守他的命令

(6) 不定式作状语

①He got up early to catch the early bus.

他起得早是为了赶上早班车

②He worked hard to catch up with the other classmates. 他努力学习是为了赶上班里其他同学

(7) 不定式作独立成分

To tell you the truth(to be honest)， I told a lie. 说实话，我撒谎了

3.不定式应该注意的考点:

(1) “疑问词 不定式”结构(疑问词直接加不定式，除why, why 要加省略to的不定式why not do)如:

l don’ t know how to choose them.

我不知道怎么选择。

I cannot decide where to go.

我决定不了去哪。

(2)不定式的否定式。如:

l decided not to go. 我决定不走

(3)不定式的完成式。如:

He seemed to have c leaned the room before l came in. 他似乎在我进来之前就打扫了房间

The boy is said to have been sent to the hospital last week.据说这个男孩上周被送进了医院

(4) tooto结构。如:

He was too excited to go to sleep. 他太兴奋以至于睡不着觉

(5)主动表被动。如:

The book is easy to read. 这本书很容易读

I have a book to read. 我有一本书要读