不定式做主语：To dance is a lot of fun 跳舞非常有趣
不定式做表语：The best plan is to leave at once.最上策的计划就是马山离开这里.
不定式做宾语：They began to read and write.他们开始读和写.
不定式做宾语补足语：Lucy told him not to cry.路希告诉他不要哭.
不定式做壮语：He came to give us a talk yesterday.他昨天来（为了）给我们做报告.
不定式做定语：Have you got anything to say?你还有什么要说的吗?