celery cabbage vs genus Brassica

celery cabbage and genus Brassica both are nouns.

Word	Noun	Adjective	Verb	Adverb
celery cabbage	Yes	No	No	No
genus Brassica	Yes	No	No	No

celery cabbage (noun)	genus Brassica (noun)
elongated head of crisp celery-like stalks and light green leaves	mustards: cabbages, cauliflowers, turnips, etc.
plant with an elongated head of broad stalked leaves resembling celery; used as a vegetable in east Asia