cattail vs swamp plant

cattail and swamp plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
cattail	Yes	No	No	No
swamp plant	Yes	No	No	No

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

cattail: tall erect herbs with sword-shaped leaves; cosmopolitan in fresh and salt marshes
swamp plant: a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath

Other hypernyms of cattail include bog plant, marsh plant.

cattail (noun)	swamp plant (noun)
tall erect herbs with sword-shaped leaves; cosmopolitan in fresh and salt marshes	a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath