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 )

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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 )