Ulmus thomasii vs elm tree

Ulmus thomasii and elm tree both are nouns.

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

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

Ulmus thomasii: tall widely distributed elm of eastern North America
elm tree: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of Ulmus thomasii include elm.

Ulmus thomasii (noun)	elm tree (noun)
tall widely distributed elm of eastern North America	any of various trees of the genus Ulmus: important timber or shade trees