nigella vs flower

nigella and flower both are nouns.

Word	Noun	Adjective	Verb	Adverb
nigella	Yes	No	No	No
flower	Yes	No	Yes	No

As nouns, flower is a hypernym of nigella; that is, flower is a word with a broader meaning than nigella:

nigella (noun)	flower (noun)
any plant of the genus Nigella	a plant cultivated for its blooms or blossoms
	reproductive organ of angiosperm plants especially one having showy or colorful parts
	the period of greatest prosperity or productivity

nigella (verb)	flower (verb)
	produce or yield flowers