melagueta pepper vs herb

melagueta pepper and herb both are nouns.

Word	Noun	Adjective	Verb	Adverb
melagueta pepper	Yes	No	No	No
herb	Yes	No	No	No

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

melagueta pepper: West African plant bearing pungent peppery seeds
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 melagueta pepper include herbaceous plant.

melagueta pepper (noun)	herb (noun)
West African plant bearing pungent peppery seeds	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