Sacramentum. This word is used by Cassian, as by other Latin writers, as the regular equivalent of the Greek, μυστήριον, and as such is applied to sacred truths equally with sacred rites. See Book V. xxxiv.: “Sacramenta scriptorum;” Conferences IX. xxxiv.: “Sacramentum resurrectionis Dominicæ.” And again and again the word is used of the mystery of the Incarnation in the books against Nestorius.