water chestnut plant vs water chestnut

water chestnut plant and water chestnut both are nouns.

Word	Noun	Adjective	Verb	Adverb
water chestnut plant	Yes	No	No	No
water chestnut	Yes	No	No	No

As nouns, water chestnut plant and water chestnut are synonyms defined as:

water chestnut plant and water chestnut: a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits

Other synonyms of water chestnut plant include caltrop.

water chestnut plant (noun)	water chestnut (noun)
a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits	edible bulbous tuber of a Chinese marsh plant
	Chinese sedge yielding edible bulb-shaped tubers
	a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits