lemon balm vs herb

lemon balm and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
lemon balm	Yes	No	No	No
herb	Yes	No	No	No

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

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

lemon balm: bushy perennial Old World mint having small white or yellowish flowers and fragrant lemon-flavored leaves; a garden escapee in northern Europe and North America
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 lemon balm include herbaceous plant.

lemon balm (noun)	herb (noun)
lemony leaves used for a tisane or in soups or fruit punches	aromatic potherb used in cookery for its savory qualities
bushy perennial Old World mint having small white or yellowish flowers and fragrant lemon-flavored leaves; a garden escapee in northern Europe and North America	a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests