celeriac vs herb

celeriac and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
celeriac	Yes	No	No	No
herb	Yes	No	No	No

As nouns, herb is a hypernym of celeriac; that is, herb is a word with a broader meaning than celeriac:

celeriac: grown for its thickened edible aromatic root
herb: a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests

Other hypernyms of celeriac include herbaceous plant.

celeriac (noun)	herb (noun)
thickened edible aromatic root of a variety of celery plant	aromatic potherb used in cookery for its savory qualities
grown for its thickened edible aromatic root	a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests