So the result is we can combine all of these as a single differential, and just like we've seen before, what that suggests is that we define another new quantity given by this expression.

结果就是我们能把所有的结果,整理成一个单一的微分，就像我们前面看到的一样，这说明我们可以利用这个式子,定义一个新的物理量。

麻省理工公开课 - 热力学与动力学课程节选