mattress vs paillasse

mattress and paillasse both are nouns.

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

As nouns, paillasse is a hyponym of mattress; that is, paillasse 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
paillasse: mattress consisting of a thin pad filled with straw or sawdust

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

mattress (noun)	paillasse (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 thin pad filled with straw or sawdust