mattress vs futon

mattress and futon both are nouns.

Word	Noun	Adjective	Verb	Adverb
mattress	Yes	No	No	No
futon	Yes	No	No	No

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

mattress: a large thick pad filled with resilient material and often incorporating coiled springs, used as a bed or part of a bed
futon: mattress consisting of a pad of cotton batting that is used for sleeping on the floor or on a raised frame

Other hyponyms of mattress include air mattress, feather bed, featherbed, paillasse, palliasse, pallet, spring mattress, tick.

mattress (noun)	futon (noun)
a large thick pad filled with resilient material and often incorporating coiled springs, used as a bed or part of a bed	mattress consisting of a pad of cotton batting that is used for sleeping on the floor or on a raised frame