And then we calculate changes, the convention is understood with respect to what is the zero, right.

然后我们计算改变,这个约定就是用来规定零点的位置的。

麻省理工公开课 - 热力学与动力学课程节选

That is the whole triumph of calculus is to know that by looking at the position now, the position slightly later and taking the ratio and bringing later as close as possible to right now, we define a quantity that we can say is the velocity at this instant.

这就得靠微积分了,通过了解它现在的位置,和一小段时间以后的位置,计算它们的比,再让时间间隔尽可能缩短,我们就定义了一个,被我们称之为瞬时速度的物理量

耶鲁公开课 - 基础物理课程节选

So, operands. Let us take expressions, get values out, we can store them away in places, but ultimately we want to do something with them, so we need to now start talking about what are the things we can do inside of Python, or any programming language, to manipulate them.

也就是运算对象，让我们看看这些表达式，然后看看里面的这些值，我们可以把他们存在计算机的任何位置中，最终目的还是要对这些值做一些操作，因此我们现在需要开始讨论,在Python里面可以做什么，来操作它们了，或者在任何编程语言里。

麻省理工公开课 - 计算机科学及编程导论课程节选