Ulmus pumila vs elm

Ulmus pumila and elm both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ulmus pumila	Yes	No	No	No
elm	Yes	No	No	No

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

Ulmus pumila: fast-growing shrubby Asian tree naturalized in United States for shelter or ornament
elm: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of Ulmus pumila include elm tree.

Ulmus pumila (noun)	elm (noun)
fast-growing shrubby Asian tree naturalized in United States for shelter or ornament	any of various trees of the genus Ulmus: important timber or shade trees
	hard tough wood of an elm tree; used for e.g. implements and furniture