What does the term 'adiabatic' refer to in thermodynamics?

The term 'adiabatic' in thermodynamics specifically refers to a process in which there is no heat exchange between the system and its surroundings. In an adiabatic process, the internal energy of the system changes as work is done on or by the system without any heat being added or removed.

The notion of 'constant enthalpy' is more closely associated with specific types of processes, such as isenthalpic processes, rather than strictly adiabatic processes. However, in the context of adiabatic processes, the focus is often on the relationship between pressure, volume, and temperature rather than strictly adhering to a constant enthalpy condition.

To clarify the connections, constant pressure describes an isobaric process, constant volume refers to an isochoric process, and constant temperature is indicative of an isothermal process. Understanding these distinct terms helps clarify why 'adiabatic' does not correlate directly with those properties, reinforcing its unique definition that focuses on the lack of heat transfer rather than maintaining any of those other thermal properties.