Dalmatic: The vestment the deacon wears over the alb on solemn occasions.

Deacon: An ordained minister who assists the Celebrant at the Liturgy of the Word and at the altar for the Liturgy of the Eucharist.

Deacons/diaconate: The diaconate is the first order or grade in ordained ministry. Any man who is to be ordained to the priesthood must first be ordained as a transitional deacon. Deacons serve in the ministry of liturgy, of the word, and of charity. The Permanent Diaconate is for men who do not plan to become ordained priests. The program is open to both married and unmarried men.

Dean/Vicar: The title of a priest appointed by the bishop to aid him in administering the parishes in a certain vicinity, called a "deanery." The function of a dean involves promotion, coordination, and supervision of the common pastoral activity within the deanery or vicariate.

Diocesan Curia: The personnel and offices assisting the bishop in directing the pastoral activity, administration and exercise of judicial power of the diocese.

Diocese: A particular church; a fully organized ecclesiastical jurisdiction under the pastoral direction of a bishop as local Ordinary.

Dispensation: An exemption from Church law.

Doxology: The response of the people acclaiming the sovereignty of God.