POSTCOMMUNIO. – In the Latin rite (Roman, Ambrosian, Gallican, and Mozarabic) it is the prayer said by the priest after Communion and the singing of the Communion antiphon by the people, introduced with *Dominus vobiscum*; hence called P. (sometimes also *Ad Communio*) already in the so-called Gelasian sacramentaries, while in the Gregorian it is found under the heading *Ad complendum* or *Ad completa*, i.e., to complete the Holy Mass.
The P. is recited, after the sacrifice has been completed, “in cornu Epistolae,” no longer in the middle of the altar. Along with the Collect and the Secreta (*Super Oblata* in the Gregorian), the P. is found in the most ancient texts of the Latin rite from the 5th–6th centuries; it has the same structure as these prayers, varies according to the feasts, and links Communion with them or with the ecclesiastical year. In the Latin rite, the P. is not so much a thanksgiving for Communion, as in Eastern liturgy, but rather a supplication that the Communion may achieve its full efficacy, be a purification from faults (*remedium, subsidium, munimentum, medicina caelestis*), a pledge of eternal life (*“redemptionis nostrae pignus,” “immortalitatis alimonia”*), and a bond of unity with Christ (*“inter eius membra numeratum, cuius corpori communicans est sanguini”*).