marsh marigold vs kingcup

marsh marigold and kingcup both are nouns.

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

As nouns, marsh marigold and kingcup are synonyms defined as:

marsh marigold and kingcup: swamp plant of Europe and North America having bright yellow flowers resembling buttercups

Other synonyms of marsh marigold include Caltha palustris, cowslip, May blob, meadow bright, water dragon.

marsh marigold (noun)	kingcup (noun)
swamp plant of Europe and North America having bright yellow flowers resembling buttercups	any of various plants of the genus Ranunculus
	swamp plant of Europe and North America having bright yellow flowers resembling buttercups