Apium graveolens dulce vs herb

Apium graveolens dulce and herb both are nouns.

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

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

Apium graveolens dulce: widely cultivated herb with aromatic leaf stalks that are eaten raw or cooked
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 dulce include herbaceous plant.

Apium graveolens dulce (noun)	herb (noun)
widely cultivated herb with aromatic leaf stalks that are eaten raw or cooked	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