nub
n. 要点；小块，结节；瘤；残根
例句
The nub of his case is that the principles of fairness and due process were breached.
他的案子的要点是法律的公正和正当程序原则都被破坏了。
《柯林斯英汉双解大词典》
Here we reach the nub of the argument.
现在我们谈到了争论的关键部分。
That, I think, is the nub of the problem.
我想那才是问题的核心。
