約定俗成

约定俗成
yuēdìngsúchéng
  1. established by popular usage (idiom); common usage agreement
  2. customary convention

CEDICT

Entry Composition

1 約定 yuēdìng
  1. to agree on sth (after discussion)
  2. to conclude a bargain
  3. to arrange
  4. to promise
  5. to stipulate
  6. to make an appointment
  7. stipulated (time, amount, quality etc)
  8. an arrangement
  9. a deal
  10. appointment
  11. undertaking
  12. commitment
  13. understanding
  14. engagement
  15. stipulation
2 俗 sú
  1. custom
  2. convention
  3. popular
  4. common
  5. coarse
  6. vulgar
  7. secular
3 成 chéng
  1. to succeed
  2. to finish
  3. to complete
  4. to accomplish
  5. to become
  6. to turn into
  7. to be all right
  8. OK!
  9. one tenth