furniture vs sleeper

furniture and sleeper both are nouns.

Word	Noun	Adjective	Verb	Adverb
furniture	Yes	No	No	No
sleeper	Yes	No	No	No

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

furniture (noun)	sleeper (noun)
furnishings that make a room or other area ready for occupancy	an unexpected hit
	tropical fish that resembles a goby and rests quietly on the bottom in shallow water
	a passenger car that has berths for sleeping
	one of the cross braces that support the rails on a railway track
	a piece of furniture that can be opened up into a bed
	pajamas with feet; worn by children
	a rester who is sleeping
	an unexpected achiever of success
	a spy or saboteur or terrorist planted in an enemy country who lives there as a law-abiding citizen until activated by a prearranged signal