water elm vs white elm

water elm and white elm both are nouns.

Word	Noun	Adjective	Verb	Adverb
water elm	Yes	No	No	No
white elm	Yes	No	No	No

As nouns, water elm and white elm are synonyms defined as:

water elm and white elm: large ornamental tree with graceful gradually spreading branches common in eastern North America

Other synonyms of water elm include American elm, rock elm, Ulmus americana.

water elm (noun)	white elm (noun)
large ornamental tree with graceful gradually spreading branches common in eastern North America	large ornamental tree with graceful gradually spreading branches common in eastern North America
Eurasian elm closely resembling the American elm; thrives in a moist environment