不定式复合结构的含义是什么????

不定式的复合结构：for...to do sth

不定式的逻辑主语明确是谁时，是不用复合结构的，即：to do sth ；否则，用复合结构。
不定式的句法作用举例如下：

1.主语:It is very important for you to study English.
2.表语:The car is for you to drive.
3.状语:The man works hard for his boss to be pleased.
4.定语：There is no need for you to go to the office.
5.宾语：I've arranged for her to see you off.