In thermodynamics, process (TR:1338) is a change in a system defined by an initial state, a final state, and the path followed. [1] A process, to note, must not be mistaken for a transformation, which is defined by only its initial state and final state. Said another way, a process, in thermodynamics, is defined as a method of operation in which specific quantities of heat and various types of mass and work are transferred across a boundary to and from the system to alter its state.
References
1. Perrot, Pierre. (1998). A to Z of Thermodynamics. Oxford University Press.