begin to do= start to do,start doing =start to do

可以这样子说.begin和start同义,可以互换,后面跟to do和doing差别也不大.但在有些情况,通常用to do.如：
①进行时态中：be beginning to do.
The water is beginning to boil.水开始沸腾起来了.
②物作主语：sth begins/began to do sth.
It begins to rain.
③与表示心理状态的词连用：begin to realize/understand.
She began to understand.她渐渐地明白了.