Other forms: nights
Night is the dark hours when most people sleep. At night, last night, all night, a cold night.
The prepositions are fixed and worth learning as a set: at night for the general time, in the night for something that happened during it, and on Friday night for a particular one. Last night takes no preposition at all. Note good night, which is a parting rather than a greeting, and that a night out means an evening's entertainment. And night as an adjective — night shift, night bus, night sky — is everywhere.
1nounnightThe dark hours between evening and morning.~70%
“It rained all night and stopped at six.”
2nounspentAn evening spent in a particular way.~30%
“Friday night is the only one that matters to him.”
Shares are an estimate: a language model read 21 sentences found in the wild and placed 20 of them on a sense (1 were unclear) — a count of our sample, not a measurement of English.
night is a period of time.
Old English niht goes back to Proto-Indo-European *nokwts, which gives Latin nox, Greek nyx and German Nacht. It is among the small set of words reconstructable to the earliest layer of the language family, which is what you would expect of something everybody has always had.
Middle English
nyght
English, today
night
From Middle English nyght. From Middle English nighte,night,nyght,niȝt,naht, from Old English niht, from Proto-West Germanic naht (“night”), from Proto-Germanic nahts (“night”), from Proto-Indo-European nókʷts (“night”). 2
Etymology from Wiktionary, CC BY-SA