knob celery vs Apium graveolens rapaceum

knob celery and Apium graveolens rapaceum both are nouns.

Word	Noun	Adjective	Verb	Adverb
knob celery	Yes	No	No	No
Apium graveolens rapaceum	Yes	No	No	No

As nouns, knob celery and Apium graveolens rapaceum are synonyms defined as:

knob celery and Apium graveolens rapaceum: grown for its thickened edible aromatic root

Other synonyms of knob celery include celeriac, celery root, root celery, turnip-rooted celery.

knob celery (noun)	Apium graveolens rapaceum (noun)
grown for its thickened edible aromatic root	grown for its thickened edible aromatic root