In physics, the word entropy has important physical implications as the amount of ``disorder'' of a system. In mathematics, a
more abstract definition is used. The (Shannon) entropy of a variable is defined as
See also Kolmogorov Entropy, Kolmogorov-Sinai Entropy, Maximum Entropy Method, Metric Entropy, Ornstein's Theorem, Redundancy, Shannon Entropy, Topological Entropy
Ott, E. ``Entropies.'' §4.5 in Chaos in Dynamical Systems.
New York: Cambridge University Press, pp. 138-144, 1993.