1．定义：具有名词、形容词及副词性质并具有时态、语态变化。

2．形式：（以do为例）
                    主动语态                            被动语态
一般时            to do                              to be done
进行时            to be doing
完成时            to have done                   to have been done
完成进行时      to have been doing

3．用法：

（1）用作主语：
To speak good English is not easy.
or: It is not easy to speak good English.
（采用形式主语 it 以避免头重脚轻）
It took me an hour to do the work.

（2）用作宾语：
She decided to take the examination.
I hope to meet him soon.

（3）宾语补足语：
They expected us to help them.
He wants his son to study hard.
金牌重点：
不定式作宾补，如谓语动词是感官动词，使役性动词（see, hear, notice, watch, make, have, let...），则不定式符号“to”须省略，但在被动语态中不能省。
I heard them sing in the classroom.
I made her clean the room.
The girl is heard to sing an English song.

（4）用作表语：
To teach is to learn.
His job is to sell cars.

（5）用作状语，表示目的，结果：
We come to school to study English.（目的）
           = in order to
I hurried to the store, only to find it closed.（结果）

（6）定语：不定式短语作定语须位于名词之后。
He asked for a piece of paper to write it on.
                  = to write it on the piece of paper.
The poor man has no house to live in.
                                         = to live in the house.
Have you anything to do?
              = to do anything

4．不定式的时态意义：
She seems to dance very well.（现在情况）
She seems to be dancing in the dancing hall.（正在进行）
She seems to have danced well.（过去情况）
Has was happy to have been staying with his uncle.（动作持续一段时间）

5．不定式语态：
The doctor [wrecommend]recommended[/w] him to air the room.
The doctor recommended the room to be aired.
She expects the police to find her bicycle.
She expects her bicycle to be found by the police.
She felt a bit puzzled as he had asked her such a question.
She felt a bit puzzled to have been asked such a question.

6．不定式否定形式：not to do ...
He got up early in order not to miss the train.

测试精编

1. Did you find out ________ the pie out of oven?
A. to take      B. have taken       C. when to take        D. being taken

2. You would be irritated if you watched the mail ________ on your desk every day.
A. putting up   B. to be put up      C. to pile up           D. pile up

3. We shall set Jim ________ the passage.
A. explaining   B. explained        C. to explain          D. explain

4. In fact, she would rather leave for San Francisco ________ in Los Angeles.
A. tostay      B. than stay         C. than staying        D. than have stayed

5. Madame Curies is believed ________ the radium.
A. discovering   B. having discovered   C. to have discovered   D. to discover

KEYS

1. C    2. D    3. C    4. B    5. C