作主语
句首
To know yourself is the beginning of all wisdom.
后置
It is +形容词+to do<br>如difficult, easy, hard, important, impossible, necessary等<br>
It is+名词+to do<br>如It is a shame/a virtue/one's responsibility/one's honor to do等<br>
It takes sb sth to do<br>如It takes sb some time to do/ It takes sb some money to do等<br>
作宾语
常见的接不定式作宾语的动词包括：decide, choose, hope，expect, <br>refuse, promise, fail, manage, plan, prepare, learn，hate, like,prefer等<br>
动词后面接不定式or 动名词？<br> 有的动词只能接动名词，如consider, enjoy, avoid, finish等• <br>有的动词只能接不定式，如decide, hope, fail, refuse等• <br>有的动词既能接动名词又能接不定式，含义没有太大差别，如begin, start, continue等<br>有的动词既能接动名词又能接不定式，但意义不同，如remember to do/remember doing
疑问词+ to do，<br>如what,who,where, how等，一起作动词的宾语<br>
She hasn't decided where to go next.
作宾补
表示指示，愿望或感觉，可以构成“动词+宾语+不定式（做宾补）”的结构，<br>包括：advise, persuade，instruct, allow, permit, remind, order, force, ask, <br>tell, wish，want, expect, let, make, have, see, hear, feel, watch等<br>
I'm gonna ask Monica to marry me
如果动词是使役动词let,make, have或者是感官动词see, hear, feel,watch, notice等，<br>此时作宾补的不定式要省略不定式符号to<br>
作定语
与所修饰的词构成主谓关系或动宾关系
I have a lot of work to do.
He is the best person to do this job
做状语
目的，结果，原因状语
目的：Eat to live, not live to eat.
结果：What have l done to make you so angry？
原因：I'm glad to see you look so well.
