gallery vs passageway

gallery and passageway both are nouns.

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

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

gallery (noun)	passageway (noun)
narrow recessed balcony area along an upper floor on the interior of a building; usually marked by a colonnade	a passage between rooms or between buildings
a covered corridor (especially one extending along the wall of a building and supported with arches or columns)	a path or channel or duct through or along which something may pass
a long usually narrow room used for some specific purpose
a room or series of rooms where works of art are exhibited
a porch along the outside of a building (sometimes partly enclosed)
a horizontal (or nearly horizontal) passageway in a mine
spectators at a golf or tennis match