What are some essential elements in the Sacrament of Holy Orders?

Catholic Answer

The essential elements in the Sacrament of Holy Orders consist of the laying on of hands by the Bishop, and the consecratory prayer.

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from The Catechism of the Catholic Church, second edition, English translation 1994

1536 Holy Orders is the sacrament though 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.

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1538 Integration into one of these bodies in the Church (Bishops, priests, and deacons) was accomplished by a rite called orinatio, 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 {Cf. Lumen Gentium10}) which can come only from Christ himself through His Church. Ordination is also called consecratio, for it is a laying on of hands by the bishop, with the consecratory prayer, constitutes the visible sign of this ordination.