dwarf elm vs elm

dwarf elm and elm both are nouns.

Word	Noun	Adjective	Verb	Adverb
dwarf elm	Yes	No	No	No
elm	Yes	No	No	No

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

dwarf elm: 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 dwarf elm include elm tree.

dwarf elm (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