elm tree vs elm

elm tree and elm both are nouns.

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

As nouns, elm tree and elm are synonyms defined as:

elm tree and elm: any of various trees of the genus Ulmus: important timber or shade trees

elm tree (noun)	elm (noun)
any of various trees of the genus Ulmus: important timber or shade trees	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