birth canal vs passageway

birth canal and passageway both are nouns.

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

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

birth canal: a passage in the uterus and vagina through which a fetus passes during vaginal birth
passageway: a path or channel or duct through or along which something may pass

Other hypernyms of birth canal include passage.

birth canal (noun)	passageway (noun)
a passage in the uterus and vagina through which a fetus passes during vaginal birth	a passage between rooms or between buildings
	a path or channel or duct through or along which something may pass