coriander plant vs herb

coriander plant and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
coriander plant	Yes	No	No	No
herb	Yes	No	No	No

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

coriander plant: Old World herb with aromatic leaves and seed resembling parsley
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 coriander plant include herbaceous plant.

coriander plant (noun)	herb (noun)
Old World herb with aromatic leaves and seed resembling parsley	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