rock elm vs elm

rock elm and elm both are nouns.

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

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

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

Other hypernyms of rock elm include elm tree.

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

rock elm: large ornamental tree with graceful gradually spreading branches common in eastern North America
elm: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of rock elm include elm tree.

rock elm (noun)	elm (noun)
tall widely distributed elm of eastern North America	any of various trees of the genus Ulmus: important timber or shade trees
large ornamental tree with graceful gradually spreading branches common in eastern North America	hard tough wood of an elm tree; used for e.g. implements and furniture