smooth-leaved elm vs elm

smooth-leaved elm and elm both are nouns.

Word	Noun	Adjective	Verb	Adverb
smooth-leaved elm	Yes	No	No	No
elm	Yes	No	No	No

As nouns, elm is a hypernym of smooth-leaved elm; that is, elm is a word with a broader meaning than smooth-leaved elm:

smooth-leaved elm: European elm with lustrous smooth leaves used as an ornamental
elm: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of smooth-leaved elm include elm tree.

smooth-leaved elm (noun)	elm (noun)
European elm with lustrous smooth leaves used as an ornamental	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