DEO GRATIAS. – A formula of greeting and thanksgiving already used by St Paul (I Cor 15:57; II Cor 2:14). St Augustine speaks of it as a distinctive word among the Christians of Africa or as a greeting and offers an explanation (*Enarr. in Ps.*, no. 6): «Fratres, cum vident homines, D. g. dicunt... Num enim non est locus gratulationis, quando se invicem vident qui habitant in Christo?»
In liturgical worship the faithful say this formula in response to the *Benedicamus Domino*; in the Roman and Ambrosian Mass after the *Ite, missa est*, in the Gallican and Mozarabic liturgies after the announcement of the title of a Lesson, and in the Divine Office after all the Lessons, formerly also after the reading of the Acts of the Martyrs, to give thanks to the Lord for the instruction received from the divine word or for the encouragement to perform good works. The celebrant on Holy Saturday says it after the announcement of the Easter chant of the Alleluia. The bishop says it when presenting candidates for diaconate and priesthood, after ascertaining their worthiness, and in the consecration of bishops and abbots, when they have made the prescribed oath of fidelity. The Supreme Pontiff formerly said it on Easter Day, after hearing the number of the newly baptized (*Ordo Romanus* I, 3), etc.