giant hyssop vs herb

giant hyssop and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
giant hyssop	Yes	No	No	No
herb	Yes	No	No	No

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

giant hyssop: any of a number of aromatic plants of the genus Agastache
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 giant hyssop include herbaceous plant.

giant hyssop (noun)	herb (noun)
any of a number of aromatic plants of the genus Agastache	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