不定式for结构在句中可以作主、宾、表、定、状、同位语：
1．It is easy for Tom to do this work．（主语）汤姆做此工作是容易的.
2．I'd like for him to come here．（宾语）我喜欢他来这里.
3．His idea is for us to travel in two different groups．（表语）他的想法是：我们分成两组旅行.
4．Have you heard about the plan for you to go abroad．（定语）你听到让你出国的计划吗?
5．The word is too difficult for him to pronounce well．（状语）这单词太难,他念不准.
6．In the most schools,it is the custom for the headmaster to declare the newterm start．在大部分学校,校长宣布新学期开始是一个习惯.
b．不定式of结构只能在句中作主语.
1．It was careless of him to leave his umbrella in the train．他把伞丢在火车上真是太粗心了.
2．It is awfully good of you to come to see me off at the station．谢谢你来车站送我.