Greek ἐντροπία - en-"within" trop-"change"
entropy /ˈɛntrəpi/ noun
1. Physics - a thermodynamic quantity representing the unavailability of a system’s thermal energy for conversion into mechanical work “the second law of thermodynamics says that entropy always increases with time”
2. lack of order or predictability; gradual decline into disorder
The degree of disorder or uncertainty in a system, which is proportional to the amount of energy no longer available to do physical work. The degredation of matter and energy in the universe towards death. It quantifies the exponential complexity of a dynamical system. Left unchecked disorder increases over time, as the entropy increases everything moves from order to disorder. Energy disperses, and systems dissolve into chaos. Entropy reflects that change.