Noun
classical thermodynamics (uncountable)
Thermodynamics that studies a thermodynamic system as an undivided whole, described by macrostate variables such as volume, pressure and temperature, instead of considering the thermodynamic system as an ensemble of moving molecules.
Classical thermodynamics main The thermodynamic definition of entropy was developed in the early 1850s by Rudolf Clausius and essentially describes how to measure the entropy of an isolated system in thermodynamic equilibrium with its parts. Source: Internet