Ordained minister who assists the celebrant at mass.

His duties include saying the Summary of the Law, the Prayers of the People, the Comfortable Words, the Dismissal, the Invocation of the Saints, and proclaiming the Gospel. He also assists with the preparation of the gifts, the Ablutions, and distributing communion.

At the altar he stands on the celebrant's right (facing the altar), and similary sits on the celebrant's right at the sedilia.

Typically there is one deacon serving at mass, but for some holy days or other special occasions there may be two. In this instance, one serves as the Deacon of the Mass (taking the deacon duties for the Liturgy of the Eucharist) and one as the Deacon of the Word (taking the deacon duties at the Liturgy of the Word). When there are two deacons, the acolyte is not required and may act as tunicled crucifer.

At a pontifical mass, when the Bishop is present and is the celebrant, there are three deacons. Two deacons act as the Bishop's chaplains and a third as the Deacon of the Mass (assisted by an acolyte and a tunicled crucifer).