nightclub vs night club

nightclub and night club both are nouns.

Word	Noun	Adjective	Verb	Adverb
nightclub	Yes	No	No	No
night club	Yes	No	No	No

As nouns, nightclub and night club are synonyms defined as:

nightclub and night club: a spot that is open late at night and that provides entertainment (as singers or dancers) as well as dancing and food and drink

Other synonyms of nightclub include cabaret, club, nightspot.

nightclub (noun)	night club (noun)
a spot that is open late at night and that provides entertainment (as singers or dancers) as well as dancing and food and drink	a spot that is open late at night and that provides entertainment (as singers or dancers) as well as dancing and food and drink