pallbearer vs mourner

pallbearer and mourner both are nouns.

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

As nouns, mourner is a hypernym of pallbearer; that is, mourner is a word with a broader meaning than pallbearer:

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

Other hypernyms of pallbearer include griever, lamenter, sorrower.

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