Term: Enthalpy

Thermodynamic quantity equal to the sum of the internal energy of a system plus the product of the pressure-volume work done on the system. Enthalpy cannot be directly measured; however, enthalpy differences between the initial and the final state points of a process can be measured.

Source: from Gatley, Understanding Psychrometrics. Related: RR-9401: Development of Moisture Storage Coatings for Enthalpy Storage Wallboard