And the first law says, well heat and work are different forms of energy, and we can add them, and the path dependence of these two things is somehow cancelled in the fact that we have this internal energy.

热力学第一定律说，热和功是能量的不同表现形式，我们可以把它们加起来,它们与路径相关的部分相互抵消,我们就有了内能。

麻省理工公开课 - 热力学与动力学课程节选