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# ENTROPY

unavailable energy or molecular disorder. Entropy is
at a maximum when the molecules in a gas are at the same energy
level. Entropy should not be confused with uncertainty.
Uncertainty is at a minimum when all elements are in the same
category. (Umpleby)

*see* statistical entropy, a measure of variation, dispersion or diversity; *see* thermodynamic entropy, a measure of usable energy. The similarity between the two types of entropy is merely formal in that both are expressed as the logarithm of a probability. The thermodynamic entropy S = k log W is a function of the dispersion W of heat, with k being Boltzmann's CONSTANT. The statistical entropy of an event a is H_a = -k log p_a where p_a is the statistical probability of a and k is arbitrarily set so as to make the logarithm dual (*see* bit). The negative sign gave rise to the notion of negentropy (Material entropy *see* pollution, social entropy). (Krippendorff)

URL= http://cleamc11.vub.ac.be/ASC/ENTROPY.html