night club vs nightclub

night club and nightclub both are nouns.

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

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

night club and nightclub: 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 night club include cabaret, club, nightspot.

night club (noun)	nightclub (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