Adiabatic

An adiabatic process, phenomenon or change is one involving two physical, chemical or biological systems in which no heat is exchanged. The definition applies in particular to the pair formed from a system and the environment external to this system: current studies on fluids, and on air in particular, are based on the division of the fluid into more or less mobile parcels of fluid; we can then ask what is the normal behaviour of the system making up a parcel of air in relation to the surrounding atmosphere, which usually forms the whole of the external medium.