动词不定式
  必定： to + V.原 或者 (to)+ V.原  否定：not/never + (to) + V.原
He likes to read novels. I saw him come. We decided not to buy that house.4)  It is interesting to fly a kite. 5)  Please let him not go there.
动词不定式结构
作主语
To hear your voice is so nice.To study hard is very important.
It is so nice to hear your voice.
It is very important to study hard.
不定式作主语时，通惯用it作形式主语，把真正主语放在后面。
注意:
1、It is +adj. for/ of sb. to do sth.
不定式做主语 谓语动词用单数