As a greeting (“Good evening, ladies and gentlemen…”)? Or as parting words (“Good night, see you in the morning”)?* I’m not sure there is s succinct way to do so in any case, but I shall make my best guesses below, by prefixing appropriate phrases with generic “hello”'s and “good-bye”'s:
[Greeting]
Good evening [Speaking to one person] Salve, bonam vesperam tibi exopto [Speaking to more than one person] Salvete, bonam vesperam vobis exopto
Good night [Speaking to one person] Salve, bonam noctem tibi exopto [Speaking to more than one person] Salvete, bonam noctem vobis exopto
(literally: Hello, I wish you a good evening/night)
[Parting]
Good evening [Speaking to one person] Vale, bonam vesperam tibi exopto [Speaking to more than one person] Valete, bonam vesperam vobis exopto
Good night [Speaking to one person] Vale, bonam noctem tibi exopto [Speaking to more than one person] Valete, bonam noctem vobis exopto
(literally: Good-bye, I wish you a good evening/night)
(* Maybe you can use just the “Bonam…exopto” parts, and rely on context to provide the meaning – Are you entering or leaving the room – But I’m not sure)
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