ANNIVERSARIUS (sc. dies), ANNIVERSARIUM: A day or service in memory of a deceased person. From the second century it was usual in Christian congregations to celebrate the death-days of their martyrs with divine service as they recurred annually. Families also used to commemorate their departed members on their death-days. From this custom arose the festivals of the martyrs and saints, as also those anniversaries for departed members of the congregations which are still held in the Roman Catholic Church; and consist in masses and alms provided for by special endowments.