slippery elm vs elm

slippery elm and elm both are nouns.

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

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

slippery elm: North American elm having rough leaves that are red when opening; yields a hard wood
elm: any of various trees of the genus Ulmus: important timber or shade trees

Other hypernyms of slippery elm include elm tree.

slippery elm (noun)	elm (noun)
North American elm having rough leaves that are red when opening; yields a hard wood	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