pistia vs aquatic plant

pistia and aquatic plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
pistia	Yes	No	No	No
aquatic plant	Yes	No	No	No

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

pistia: pantropical floating plant forming a rosette of wedge-shaped leaves; a widespread weed in rivers and lakes
aquatic plant: 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 pistia include hydrophyte, hydrophytic plant, water plant.

pistia (noun)	aquatic plant (noun)
pantropical floating plant forming a rosette of wedge-shaped leaves; a widespread weed in rivers and lakes	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