water plantain vs swamp plant

water plantain and swamp plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
water plantain	Yes	No	No	No
swamp plant	Yes	No	No	No

As nouns, swamp plant is a hypernym of water plantain; that is, swamp plant is a word with a broader meaning than water plantain:

water plantain: marsh plant having clusters of small white or pinkish flowers and broad pointed or rounded leaves
swamp plant: a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath

Other hypernyms of water plantain include bog plant, marsh plant.

water plantain (noun)	swamp plant (noun)
marsh plant having clusters of small white or pinkish flowers and broad pointed or rounded leaves	a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath