The spoken use of "night" as an informal, common version of "good night" (wishing 1 a restful sleep) is popular, but I am unsure what the correct composed equivalent is - if there is a single. I have often utilized 'Night having an apostrophe, normally capitalized: By way of example, https://beckettetozk.blogozz.com/36860551/the-basic-principles-of-night-gangnam-퍼펙트가라오케-karaoke-guide