to 不定詞の名詞的用法

名詞は主語、目的語、補語で利用する。

主語：
    To buy a car is my target this year.

不定詞が主語で使うとき、大抵 it を使って文章の形を言いやすいように整える。
　 It is my target to buy a car this year.

   It is easy to use.
 
   It is difficult for me to understand this theory.

補語：
　The purpose is to let him more stronger.

  My dream is to become a pilot.

目的語：
　I find it difficult to understand this theory.
　
　I know that easy to use.