cowslip vs kingcup

cowslip and kingcup both are nouns.

Word	Noun	Adjective	Verb	Adverb
cowslip	Yes	No	No	No
kingcup	Yes	No	No	No

As nouns, cowslip and kingcup are synonyms defined as:

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

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

cowslip (noun)	kingcup (noun)
early spring flower common in British isles having fragrant yellow or sometimes purple flowers	any of various plants of the genus Ranunculus
swamp plant of Europe and North America having bright yellow flowers resembling buttercups	swamp plant of Europe and North America having bright yellow flowers resembling buttercups