mattress vs featherbed

mattress and featherbed both are nouns.

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

As nouns, featherbed is a hyponym of mattress; that is, featherbed 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
featherbed: a mattress stuffed with feathers

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

mattress (noun)	featherbed (noun)
a large thick pad filled with resilient material and often incorporating coiled springs, used as a bed or part of a bed	a mattress stuffed with feathers

mattress (verb)	featherbed (verb)
	hire more workers than are necessary
	treat with excessive indulgence