columbarium vs cinerarium

columbarium and cinerarium both are nouns.

Word	Noun	Adjective	Verb	Adverb
columbarium	Yes	No	No	No
cinerarium	Yes	No	No	No

As nouns, columbarium and cinerarium are synonyms defined as:

columbarium and cinerarium: a niche for a funeral urn containing the ashes of the cremated dead

columbarium (noun)	cinerarium (noun)
a sepulchral vault or other structure having recesses in the walls to receive cinerary urns	a niche for a funeral urn containing the ashes of the cremated dead
a niche for a funeral urn containing the ashes of the cremated dead
a birdhouse for pigeons