mezzanine floor vs storey

mezzanine floor and storey both are nouns.

Word	Noun	Adjective	Verb	Adverb
mezzanine floor	Yes	No	No	No
storey	Yes	No	No	No

As nouns, storey is a hypernym of mezzanine floor; that is, storey is a word with a broader meaning than mezzanine floor:

mezzanine floor: intermediate floor just above the ground floor
storey: a structure consisting of a room or set of rooms at a single position along a vertical scale

Other hypernyms of mezzanine floor include floor, level, story.

mezzanine floor (noun)	storey (noun)
intermediate floor just above the ground floor	a structure consisting of a room or set of rooms at a single position along a vertical scale