Apium graveolens vs herb

Apium graveolens and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
Apium graveolens	Yes	No	No	No
herb	Yes	No	No	No

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

Apium graveolens: herb of Europe and temperate Asia
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 Apium graveolens include herbaceous plant.

Apium graveolens (noun)	herb (noun)
herb of Europe and temperate Asia	aromatic potherb used in cookery for its savory qualities
	a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests