I talked about this concept of mole here.

我谈论摩尔的概念。

youdao

The beautiful concept always unites with rareness. Such as the mole of beauty on a girl's face, there is very goodlooking one, there is one pile very troublesome.

美的概念总是同稀少联在一起。例如一个姑娘脸上的美人痣，有一颗很好看，有一堆就很麻烦。

youdao

I talked about this concept of mole here.

我谈论摩尔的概念。

麻省理工公开课 - 固态化学导论课程节选