heading vs passageway

heading and passageway both are nouns.

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

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

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