Pastinaca sativa vs herb

Pastinaca sativa and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pastinaca sativa	Yes	No	No	No
herb	Yes	No	No	No

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

Pastinaca sativa: a strong-scented plant cultivated for its edible 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 Pastinaca sativa include herbaceous plant.

Pastinaca sativa (noun)	herb (noun)
a strong-scented plant cultivated for its edible root	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