To go to school(主语)is his dream.上学是他的梦想。
To go to school and to stay away from his cruel father(并列主语)ale were what he expected-他期望能去上学，远离他残忍的父亲。
2.跟在名词后面作定语，如：
the ability to operate the machine操作机器的能力the first(second...1ast)people to speak第一个(第2个，…最后一个)发育的人
3.跟在be动词的后面作表语，如：
What 1 want to do is to have a sightseeing(表语)around Be.jing.我想做的是在北京观光旅行。
4.跟在及物动词的后面作其宾语
I enjoy talking to you.(宾语)能和你谈话我真高兴。
They dont permit smoking(宾语)in the public places.他们不允许在公众场合吸烟。
5.对宾语的性质，特征等进行补充说明，作宾语补足语，如：
We have persuaded him to accept our proposal.一(宾语补足语)我们已经说服他接受了我们的建议。
在使役动词和感官动词的后面常带不to的不定式结构作宾语补足语：
have(let/make/feel/hear/watch/see/observe)sb.do sthhelp sb.do sth.
6.作状语。不定式结构在句子中通常充当结果状语和目的状语。如：
He spent much time on his studies to be a top student.一(目的状语)为了成为班上的优等生，他在学习上花了很多的时间He came there to find his friends had left.(结果状语)他到了那里结果发现他的朋友已经走了。
7.作为主语补足语，补充说明主语的性质，特征等，如：
He is supposed to come here(主语补足语)tomorrow.他应该明天到这里。
He is said to have great talent for art.(主语补足语)据说他在艺术方面很有才华。
8.常接不定式作宾语的动词：
agree，afford，aim，arrange，appear，ask，attempt，choose，claim，decide，desire，determine.expect，fail，guarantee，hope，endeavor，intend，long，mean，manage，offer，，plan，pledge，pretend，promise，proceed，prove，resolve，refuse，request，swear，tend，try，wait，wish
9.不定式的习惯用法：
句型：cannot choose but docanl help but