The spoken usage of "night" as an informal, common version of "great night" (wishing one particular a restful sleep) is frequent, but I am undecided what the appropriate written equivalent is - when there is 1. I've usually applied 'Night by having an apostrophe, ordinarily capitalized: By way of example, https://jaredf2q53.blogrelation.com/44305610/facts-about-night-gangnam-퍼펙트가라오케-karaoke-guide-revealed