passageway vs heading

passageway and heading both are nouns.

Word	Noun	Adjective	Verb	Adverb
passageway	Yes	No	No	No
heading	Yes	No	No	No

As nouns, heading is a hyponym of passageway; that is, heading is a word with a more specific, narrower meaning than passageway:

Other hyponyms of passageway include aisle, gangway, arcade, areaway, corridor, drift, gallery, gangway, gate, shaft, tunnel, walk-through.

passageway (noun)	heading (noun)
a passage between rooms or between buildings	a horizontal (or nearly horizontal) passageway in a mine
a path or channel or duct through or along which something may pass	a line of text serving to indicate what the passage below it is about
	the direction or path along which something moves or along which it lies