good-night
UK[ˌɡʊd ˈnaɪt]US[ˌɡʊd ˈnaɪt]
interj
a conventional expression used on parting at night or before going to sleep.
n
an instance of saying "good night"; a farewell for the night.
Etymology
the phrase "good night" emerged in middle english as a conventional parting wish. its components are deeply rooted in the germanic linguistic tradition: "good" derives from old english gōd, meaning "virtuous, desirable, valid," from proto-germanic gōdaz, and ultimately from proto-indo-european gʰedʰ-, "to unite, be associated, suitable." "night" comes from old english niht, from proto-germanic nahts, tracing back to the proto-indo-european root nókʷts, "night." the literal sense of the wish is for a "good" or "beneficial" period of "night" for the person addressed. over time, this transparent compound solidified into a standard, unanalyzed formula for evening farewells, losing its compositional literalness in everyday use.
Analysis
this is a compound phrase formed from two independent english words, 'good' and 'night'. it functions as a fixed lexical unit.
Examples
she kissed her children and whispered, "good-night."
he gave a cheerful good-night to everyone before heading upstairs.
we exchanged good-nights and went to our separate rooms.