1.不定式作表语
不定式可放在be动词后边,构成表语。例如:
My work is to clean the room every day.
His dream is to be a doctor.
2.不定式作定语
不定式做定语一般要放在被润饰的词后。例如:
I have a lot of work to do.
So he made some candles to give light.
3.不定式作状语
1)意图状语
To… only to (只是为了),in order to,so as to,so(such)… as to… (如此……以便……)
He ran so fast as to catch the first bus. 他飞快地跑以便赶上第一班车。
I come here only to say good-bye to you. 我来只是是向你离别。
2)作成绩状语,表事前没有预料到的,要放在语句后边。当动词与介词连用时,常坐落"形容词+动词不定式"结构的结尾。