We'll then look at the quantity, internal energy, which we define through the first law, and we think of it as a function of two variables T and V.

接下来我们考虑内能，这是由热力学第一定律定义的物理量，我们把它看作T和V的函数。

麻省理工公开课 - 热力学与动力学课程节选