一．不定式

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. joozone.com