You are no boy.

题目

You are no boy.
是否等于You are not a boy.
NO也等于not a

答案

等于
但no语气比not a语气更重一些
You're no boy.主要体现出说话者看不起那个人,所以用no更恰当.
相关举例：
I realized that was no beautiful fish.
I realized that was not a beautiful fish.
自己念一下,第一句更具有强调作用