red elm vs Ulmus rubra

red elm and Ulmus rubra both are nouns.

Word	Noun	Adjective	Verb	Adverb
red elm	Yes	No	No	No
Ulmus rubra	Yes	No	No	No

As nouns, red elm and Ulmus rubra are synonyms defined as:

red elm and Ulmus rubra: North American elm having rough leaves that are red when opening; yields a hard wood

Other synonyms of red elm include slippery elm.

red elm (noun)	Ulmus rubra (noun)
North American elm having rough leaves that are red when opening; yields a hard wood	North American elm having rough leaves that are red when opening; yields a hard wood
autumn-flowering elm of southeastern United States