second law of thermodynamics(redirected from 2nd law of thermodynamics)
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sec·ond law of ther·mo·dy·nam·ics
the entropy of the universe moves toward a maximum; similarly, the entropy of any isolated microcosm (for example, a chemical reaction) proceeds spontaneously only in that direction that yields an increase in entropy, entropy being maximal at equilibrium. To quote G.N. Lewis, "Every process that occurs spontaneously is capable of doing work; to reverse any such process requires the expenditure of work from the outside."