negentropy
The difference between the entropy of a system and the maximum possible entropy of the same system.
countable, uncountable
The same magnitude, but with a minus sign, i.e., the measure of macroscopic ordering, the measure of non-uniformity in the distribution of heat, the measure of the differences in temperature—temperature gradients—is called negentropy.
The difference between the entropy of a probability distribution and the maximum possible entropy of the same probability distribution.
countable, uncountable
Brillouin (1956) made an attempt to link thermodynamic notions to the notions of information theory. To this end he employs the idea of bound information or information consistent with some microstates of a physical system. […] Brillouin has shown that bound information is equal to entropy decrease or negentropy increase. This is a so called negentropy principle of information, according to which negentropy can be turned into information and vice versa as follows from (1.103).
Where it comes from
From nega- + entropy. A blend of negative + entropy, coined by the French physicist Léon Brillouin (1889–1969). The term negative entropy was introduced by the Austrian physicist Erwin Schrödinger (1887–1961) in his book What is Life? (1944, based on lectures delivered in February 1943).
Adapted from the Wiktionary entry negentropy (CC BY-SA 4.0).