good day

interjection

1. a conventional expression used at meeting or parting during the daytime.

good day

1. a conventional expression of greeting or farewell used during the day

Word History and Origins

Origin of good day¹

Middle English word dating back to 1175–1225

Idioms and Phrases

Also,. Formal ways of saying “Hello” or “Goodbye.” For example, He began rather oddly by addressing the audience with “Good day,” or “Good afternoon, ladies,” said the sales clerk as we walked out. All these greetings represent an abbreviation of the now obsolete God give you a good day (afternoon, etc.), which dates from about 1200. Also see good night.