IPA: /kəˈlʌmbəˌrɪəm/
KK: /kəˈlʌmbəˌrɪəm/
A structure that has small spaces or niches to hold urns containing the ashes of people who have been cremated.
The family decided to place their loved one's ashes in a columbarium.
Columbarium is formed from "columba" (meaning dove) and the suffix "-arium" (meaning a place for). The word refers to a place for doves, which metaphorically represents a structure for housing urns containing ashes of the deceased, akin to doves being housed in a dovecote.
Imagine a place where doves are kept ('columba') — that's why a columbarium is a place for holding urns of ashes.