So, in the language of calculus, x is a function of time and this is a particular function.

所以,从微积分的角度来看,x是一个关于时间的函数,而且是个很特殊的函数

耶鲁公开课 - 基础物理课程节选

- The fact that I've called it X, is really just a programming -- it's a feature of the programming language that I, the human, can now refer to it.

事实是我叫它为X，它实际上只是一个程序-,它是程序的一个特写，我们可以参考使用它。

哈佛公开课 - 计算机科学课程节选