Ulmus crassifolia vs elm tree

Ulmus crassifolia and elm tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ulmus crassifolia	Yes	No	No	No
elm tree	Yes	No	No	No

As nouns, elm tree is a hypernym of Ulmus crassifolia; that is, elm tree is a word with a broader meaning than Ulmus crassifolia:

Ulmus crassifolia: elm of southern United States and Mexico having spreading pendulous corky branches
elm tree: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of Ulmus crassifolia include elm.

Ulmus crassifolia (noun)	elm tree (noun)
elm of southern United States and Mexico having spreading pendulous corky branches	any of various trees of the genus Ulmus: important timber or shade trees