It turns out that when you're talking about macroscopic properties of matter, you don't need very many variables to describe the system completely thermodynamically.

实际上,当你谈及物质的宏观性质时，你并不需要很多变量才能从热力学上,完整地描述这个系统，’

麻省理工公开课 - 热力学与动力学课程节选