late at night

a night owl (idiomatic)

(euphemistic) job in the nightlife / sex industry

(Internet slang, humorous, pun) Christmas Eve, as a night of sexual activity between young couples

(collective, literally) a thousand nights / (archaic, figuratively, collective) lots of nights; an innumerable number of nights

a female given name

an agent that preservers food by preventing the growth of microorganisms; a preservative

antibiotics

bleach, bleacher

(medicine) anesthetic, anaesthetic