marsh plant vs hydrophyte

marsh plant and hydrophyte both are nouns.

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

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

marsh plant: a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath
hydrophyte: a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth

Other hypernyms of marsh plant include aquatic plant, hydrophytic plant, water plant.

marsh plant (noun)	hydrophyte (noun)
a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath	a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth