Eucharist (Gr. eucharistia, thanksgiving), the name given to the Blessed Sacrament of the Altar under its twofold aspect of sacrament and Sacrifice of the Mass, and in which, whether as sacrament or sacrifice, Jesus Christ is truly present under the appearances of bread and wine. Other titles acn be used, such as the "Lord's Supper," or "Table of the Lord."

The Church honors the Eucharist as one of her most exalted mysteries, as it yields nothing when allied to the mysteries of the Trinity and Incarnation. These three mysteries constitute a wonderful triad, which causes the essential characteristic of Christianity, as a religion of mysteries far transcending the capabilities of reason, to shine forth in all its brilliance and splendor.