动词不定式是整个中学阶段英语语法的重点之一，它属于非谓语动词。很多人不理解“不定式”三个字是什么意思。其实徐老师认为其意应该是“不受人称、数量和时态等条件限定的动词形式”，简称“不定式”。其格式是to 动词原形。
一、不定式的格式
虽然不定式不受人称、数量和时态等的限制，但是它还是有自己的不同格式的。
1、一般式：to do 例：I have a lot of work to do, so I can’t go swimming.
2、否定式：not to do例：Nobody is allowed to leave this room until the thief has been caught.
3、进行式：to be doing例：He pretended to be reading when the teacher came in.
4、完成式：to have done例：I’m sorry to have lost your book.
5、被动式：to be done/to have been done例：Tom has a bicycle to be repaired.
6、完成进行式：to have been doing例：Tom seemed to have been waiting for a long time.
7、省略式：to例：If you don’t want to go to shanghai, you don’t have to(go to shanghai).
二、不定式的用法
不定式既然是非谓语动词之一，它当然不能充当谓语，但是它的用途还是非常广的。它具有名词、形容词、副词的特性和作用，所以不定式可以做主语、宾语、宾语补语、表语、定语和状语等。
1、做主语
To get up early is necessary.
It is interesting to play with snow in winter.
It is important for a teacher to keep his mind sharp.
2、做宾语
We decided to buy a new house.
As a policeman, Tom felt it his duty to help the homeless.
3、做宾语补语
Tom considers John to be his blood brother.
He asked me to go with him.
4、做表语
To do two things at a time is to do neither.
Your task next week is to finish the program.
5、做定语
I am sure that he has the ability to make complicated things easy and clear.
Tom was so tired that he didn’t have the strength to pick up the phone.
6、做状语
I arrived early this morning to get ready before the meeting.
Tom hurried to the cinema only to find it was closed.
,
