Enthalpy 

In thermodynamics, enthalpy (/ˈɛnθəlpi/; from Greek ἐν- en- “in” and θάλπος thalpos “warmth”) is a property of a system that is the sum of the internal energy of the system and the product of its volume and pressure. In short, it is a measure of how much heat energy is in a system. The SI unit of enthalpy is the joule.