kingcup vs marsh plant

kingcup and marsh plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
kingcup	Yes	No	No	No
marsh plant	Yes	No	No	No

As nouns, marsh plant is a hypernym of kingcup; that is, marsh plant is a word with a broader meaning than kingcup:

kingcup: swamp plant of Europe and North America having bright yellow flowers resembling buttercups
marsh plant: a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath

Other hypernyms of kingcup include bog plant, swamp plant.

kingcup (noun)	marsh plant (noun)
any of various plants of the genus Ranunculus	a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath
swamp plant of Europe and North America having bright yellow flowers resembling buttercups