geranium vs herb

geranium and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
geranium	Yes	No	No	No
herb	Yes	No	No	No

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

geranium: any of numerous plants of the family Geraniaceae
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 geranium include herbaceous plant.

geranium (noun)	herb (noun)
any of numerous plants of the family Geraniaceae	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