優勝劣汰 [优胜－－]

Jyutping jau1 sing3 lyut3 taai3
Pinyin yōu shèng liè tài

Definitions (CC-CEDICT)
  1. survival of the fittest (idiom)
Definitions (Wiktionary)
  1. phrase, idiomatic
    the superior win and remain and the inferior is eliminated; survival of the fittest