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Negative feedback is a basic concept of cybernetics; it is the basis of regulation and control. It is important in engineering and physiology. In biology and physiology negative feedback is known as homeostasis.
Negative feedback occurs when the output of a system acts to oppose changes to the input of a system. This has the result that the changes are made less, and the system kept within limits. The classic example is a central heating system which cuts off when a (suitably placed) temperature sensor hits a pre-set mark. The negative feedback part is the thermostat.
Homeostasis  was defined by Claude Bernard and later by Walter Bradford Cannon in 1926, 1929 and 1932 is the property of a system, either open or closed, that regulates its internal environment and tends to maintain a stable, constant condition. The concept came from that of milieu interieur which was created by Claude Bernard and published in 1865.
- Raven P.H. & Johnson G.B. 1999. Biology. 5th ed, Boston: Hill. p1058
- from Greek: ὅμοιος, hómoios, "similar" ὅμοιος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus and στάσις, stásis, "standing still"; στάσις, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- Cannon W.B. 1929. Physiological regulation of normal states: some tentative postulates concerning biological homeostatics. in: A. Pettit (ed) A Charles Richet: ses anims, ses collegues, ses élvès, p91. Paris: editions Medicales.
- Cannon W.B. 1929. Organization For physiological homeostasis. Physiol Rev. 9: 399-431.
- Cannon W.B. 1932. The wisdom of the body. W.W. Norton, New York.