The one that is at equilibrium, there is only one macroscopic state at equilibrium.

处于平衡的状态，并且只有一个平衡的宏观状态。

麻省理工公开课 - 热力学与动力学课程节选

So it applies to macroscopic systems that are in equilibrium, and how to go from one equilibrium state to another equilibrium state, and it's entirely empirical in its foundation.

因此，热力学研究的是平衡态的宏观系统,以及如何从,一个平衡态过渡到另一个平衡态，它完全是建立在经验的基础上的。

麻省理工公开课 - 热力学与动力学课程节选