同学你好，该知识点来自沪江网校《新概念英语2、3册连读【随到随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
1.作主语
可以直接作主语。如：
To see is to believe.
但在英语中，常用it作形式主语，真正的主语即动词不定式放在后面。如：
It's wrong to play tricks on other people.
It's our duty to keep our environment clean and tidy.

2.作宾语
want，decide ，agree等动词后面跟不定式。如：
We agreed to start early.
She wants to be a doctor.

3.作宾语补足语
tell，ask，want，order，teach，invite，warn，wish，help，get等词后面常接不定式作宾补。如：
I tell him not to go there by bus.
Edison's mother taught him to read and write.

4.作定语：放在被修饰的名词、代词后面
I have a lot of work to do.
The doctor said he could do nothing to help the boy.

5.表语：放在连系动词be后面
His wish is to become a scientist.

6.作状语
a.目的状语：放在go，come，use，live，in order等词后面。如：
I come to see you.
He runs fast in order to get there in time.
b.原因状语：放在sorry，glad，surprised， disappointed，excited等词后面。如：
I am glad to see you here.
I am sorry to trouble you.


祝同学学习进步~