1. The tendency of an open system toward increasing order and complexity.
2. A comparative measure of average information i.e. the efficiency of a communication system in transmitting information. The efficiency measure of the transmission of information in a communications system is statistically akin to the measure of negentropy. The measure of noise in a communication system or transmitted message is akin to the statistical measure of entropy. Negative entropy in communications may also be described as the statistical measure of the probability of meaningful information, and in cybernetic terms, of the probability of order or control. All the most important principles of statistical mechanics can be deduced from the concepts of entropy in information-communication theory.
3. In the philosophy of science the theses of information as a fundamental universal property of matter.