Enthalpy is defined by Merriam-Webster’s Collegiate Dictionary as “the sum of the internal energy of a body or system and the product of its volume multiplied by the pressure,” with “internal energy” referring to that energy required to create the system or body and the “product of its volume multiplied by the pressure” describing the amount of energy needed to displace its environment and establish its volume and pressure in order to make room for the system or body.

Salem Press Encyclopedia, 2023. 3p.