mourner vs bearer

mourner and bearer both are nouns.

Word	Noun	Adjective	Verb	Adverb
mourner	Yes	No	No	No
bearer	Yes	No	No	No

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

mourner: a person who is feeling grief (as grieving over someone who has died)
bearer: one of the mourners carrying the coffin at a funeral

Other hyponyms of mourner include pallbearer, wailer, weeper.

mourner (noun)	bearer (noun)
a person who is feeling grief (as grieving over someone who has died)	a messenger who bears or presents
	one of the mourners carrying the coffin at a funeral
	the person who is in possession of a check or note or bond or document of title that is endorsed to him or to whoever holds it
	someone whose employment involves carrying something