THE SACRAMENT OF HOLY ORDERS [from the Catechism of the Catholic Church]
1536 Holy Orders is the sacrament through which the mission entrusted by Christ to his apostles continues to be exercised in the Church until the end of time: thus it is the sacrament of apostolic ministry. It includes three degrees: episcopate, presbyterate, and diaconate.
(On the institution and mission of the apostolic ministry by Christ, see above, no. 874 ff. Here only the sacramental means by which this ministry is handed on will be treated.)
WHY IS THIS SACRAMENT CALLED “ORDERS”?
1537 The word order in Roman antiquity designated an established civil body, especially a governing body. Ordinatio means incorporation into an ordo. In the Church there are established bodies which Tradition, not without a basis in Sacred Scripture,4 has since ancient times called taxeis (Greek) or ordines. And so the liturgy speaks of the ordo episcoporum, the ordo presbyterorum, the ordo diaconorum. Other groups also receive this name of ordo: catechumens, virgins, spouses, widows,. . . .
1538 Integration into one of these bodies in the Church was accomplished by a rite called ordinatio, a religious and liturgical act which was a consecration, a blessing or a sacrament. Today the word “ordination” is reserved for the sacramental act which integrates a man into the order of bishops, presbyters, or deacons, and goes beyond a simple election, designation, delegation, or institution by the community, for it confers a gift of the Holy Spirit that permits the exercise of a “sacred power” (sacra potestas)5 which can come only from Christ himself through his Church. Ordination is also called consecratio, for it is a setting apart and an investiture by Christ himself for his Church. The laying on of hands by the bishop, with the consecratory prayer, constitutes the visible sign of this ordination.
THE THREE DEGREES OF THE SACRAMENT OF HOLY ORDERS
1554 “The divinely instituted ecclesiastical ministry is exercised in different degrees by those who even from ancient times have been called bishops, priests, and deacons.”32 Catholic doctrine, expressed in the liturgy, the Magisterium, and the constant practice of the Church, recognizes that there are two degrees of ministerial participation in the priesthood of Christ: the episcopacy and the presbyterate . The diaconate is intended to help and serve them. For this reason the term sacerdos in current usage denotes bishops and priests but not deacons. Yet Catholic doctrine teaches that the degrees of priestly participation (episcopate and presbyterate) and the degree of service (diaconate) are all three conferred by a sacramental act called “ordination,” that is, by the sacrament of Holy Orders:
Let everyone revere the deacons as Jesus Christ, the bishop as the image of the Father, and the presbyters as the senate of God and the assembly of the apostles. For without them one cannot speak of the Church.33