root canal vs passageway

root canal and passageway both are nouns.

Word	Noun	Adjective	Verb	Adverb
root canal	Yes	No	No	No
passageway	Yes	No	No	No

As nouns, passageway is a hypernym of root canal; that is, passageway is a word with a broader meaning than root canal:

root canal: the passage in the root of a tooth through which its nerve and blood vessels enter the pulp cavity
passageway: a path or channel or duct through or along which something may pass

Other hypernyms of root canal include passage.

root canal (noun)	passageway (noun)
the passage in the root of a tooth through which its nerve and blood vessels enter the pulp cavity	a passage between rooms or between buildings
	a path or channel or duct through or along which something may pass