# Entropy

Written by Jerry Ratzlaff on . Posted in Thermodynamics

Entropy, abbreviated as S, (English unit $$\frac{Btu}{lbm-R}$$, Metric unit $$\frac{kJ}{kg-K}$$), measures the unavailable energy in a heat system.  It is a measure of the disorder of a system and of its constituent molecules.  In thermodynamics it is a measure of the unavailability of a system's energy fo do work.