survival of the fittest
    n 1: a natural process resulting in the evolution of organisms
         best adapted to the environment [syn: survival, survival
         of the fittest, natural selection, selection]

Survival \Sur*viv"al\, n. [From Survive.]
   1. A living or continuing longer than, or beyond the
      existence of, another person, thing, or event; an
      outliving.
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   2. (Arhaeol. & Ethnol.) Any habit, usage, or belief,
      remaining from ancient times, the origin of which is often
      unknown, or imperfectly known.
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            The close bearing of the doctrine of survival on the
            study of manners and customs.         --Tylor.
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   Survival of the fittest. (Biol.) See Natural selection,
      under Natural.
      [1913 Webster] Survivance