Negentropy

An isolated system contains negentropy if it reveals a possibility for doing mechanical or electrical work: […] A tank of compressed gas in a room at atmospheric pressure, a vacuum tank in a similar room, a charged battery, any device that can produce high grade energy (mechanical work) or be degraded by some irreversible process (thermal conduction, electrical resistivity, friction, viscosity) is a source of negentropy. […] If a living organism needs food, it is only for the negentropy it can get from it, and which is needed to make up for the losses due to mechanical work done, or simple degradation processes in the living system. Energy contained in food does not really matter, since energy is conserved and never gets lost, but negentropy is the important factor.

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.

Negentropy is the difference between the entropy of a system and the entropy of the same system at equilibrium (i.e., when it has its maximum possible entropy). Since entropy measures the amount of disorder, negentropy measures order.

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).