de ri·gueur
adjective/də rɪˈɡɜː(r)/
/də rɪˈɡɜːr/
[not before noun] (from French)- considered necessary if you wish to be accepted socially
合乎礼节；按照习俗；按照时尚 - Evening dress is de rigueur at the casino.
按照习俗在赌场要穿晚礼服。
Word Originmid 19th cent.: French, literally ‘in strictness’. - Evening dress is de rigueur at the casino.