comforter vs eiderdown

comforter and eiderdown both are nouns.

Word	Noun	Adjective	Verb	Adverb
comforter	Yes	No	No	No
eiderdown	Yes	No	No	No

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

comforter: bedding made of two layers of cloth filled with stuffing and stitched together
eiderdown: a soft quilt usually filled with the down of the eider

Other hyponyms of comforter include continental quilt, duvet, patchwork, patchwork quilt.

comforter (noun)	eiderdown (noun)
bedding made of two layers of cloth filled with stuffing and stitched together	down of the eider duck
device used for an infant to suck or bite on	a soft quilt usually filled with the down of the eider
a person who commiserates with someone who has had misfortune
a person who reduces the intensity (e.g., of fears) and calms and pacifies