If you have a quantity which is constant over any closed path, that quantity is a thermodynamics state function.

如果有一个物理量，对任何闭合回路积分是常数，这个物理量就是一个热力学态函数。

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The state function, entropy, is introduced by the means of a perfect gas behavior, and the second law of thermodynamics is demonstrated based on the first law.

本文以理想气体的行为为手段引出熵函数，并以热力学第一定律为基础，论证了熵增大原理。

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If you have a quantity which is constant over any closed path, that quantity is a thermodynamics state function.

如果有一个物理量,对任何闭合回路积分是常数，这个物理量就是一个热力学态函数。

麻省理工公开课 - 热力学与动力学课程节选