sneezeweed vs herb

sneezeweed and herb both are nouns.

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

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

sneezeweed: any of various plants of the genus Helenium characteristically causing sneezing
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 sneezeweed include herbaceous plant.

sneezeweed (noun)	herb (noun)
any of various plants of the genus Helenium characteristically causing sneezing	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