約定俗成

Simplified: 约定俗成

On the HSK 7-9 vocabulary list, at CEFR level C2.

yuēdìngchéng ㄩㄝ ㄉㄧㄥˋ ㄙㄨˊ ㄔㄥˊ

    • established by popular usage (idiom) common usage agreement
    • customary convention

Character by character

Sources