- noun a measure of the energy in a system or process that is unavailable to do work
- noun a measure of the degree of disorder in a closed system
- A measure of the disorder of a system, such as the universe. The more order a system has, the less its entropy. The greater the entropy in a system, the lesser its energy available to do work.
- In communications, a measure of the information contained in a signal, or of transmission efficiency.
- noun the proportion of words in a piece of communication which are meaningful.
Origin & History of “entropy”
The term entropy was coined (as entropie) in 1865 by the German physicist Rudolph Clausius (1822–1888), formulator of the second law of thermodynamics. It was he who developed the concept of entropy (a measure of the disorder of a system at atomic or molecular level), and he created the name for it (on the model of energy) from Greek en- ‘in’ and tropḗ ‘turning, transformation’ (source of English trophy and tropical). The first record of the English version of the word is from 1868.