What is the difference between an ordinary, auxiliary, and coadjutor bishop?

Our Lord entrusted His authority to His apostles.  At the Ascension, He said to them, “Full authority has been given to me both in Heaven and on earth; go, therefore, and make disciples of all the nations.  Baptize them in the name ‘of the Father, and of the Son, and of the Holy Spirit.’  Teach them to carry out everything I have commanded you.  And know that I am with you always, until the end of the world.” (Matthew 28:18-20).  In this commission, our Lord imparted to them His three-fold office of Priest, Prophet, and King with the respective duties of sanctifying, teaching, and ruling.  Filled with the great gifts of the Holy Spirit poured out at Pentecost, the apostles fulfilled these offices and exercised the authority Christ had entrusted to them.

The apostles, the first bishops, handed on their office and authority to their successors through the Sacrament of Holy Orders.  Therefore, when a priest is ordained as a bishop, he receives the fullness of the Sacrament of Holy Orders, i.e. the fullness of the office and authority entrusted to the apostles: The Dogmatic Constitution on the Church of the Vatican Council II stated, “In the person of the bishops, then, to whom the priests render assistance, the Lord Jesus Christ, supreme High Priest, is present in the midst of the faithful” (#21).  Always keep in mind that our Church possesses an unbroken line of apostolic succession, meaning that the office and authority granted by Christ to the apostles (the first bishops) was transmitted to their successor bishops, and onto succeeding bishops through the ages to this present time.

A bishop is entrusted by the Holy Father with the care of the faithful of a particular place or territory, namely a diocese.  For example, Bishop Loverde is responsible for the care of the faithful in the Diocese of Arlington.  While the Pope has full, supreme, and universal power and jurisdiction over the whole Church, a bishop has power and jurisdiction over his own diocese: “This power, which they exercise personally in the name of Christ, is proper, ordinary, and immediate, although its exercise is ultimately controlled by the supreme authority of the Church…” (#27).   For this reason, the bishop of a diocese is technically called “the Ordinary.”

The bishop, acting as a successor of the apostles, is truly a representative of Christ and a sign of unity both within the diocesan church and with the church universal.  Each bishop must fulfill the three-fold office of Priest, Prophet, and King with its duties of sanctifying, teaching, and ruling.  The bishop as “the steward of the grace of the supreme priesthood” (#26) must sanctify his people through the offering of the sacraments, especially the Holy Eucharist.  As a teacher, the bishop must preach the Gospel, teach as a real witness to the divine and Catholic truth (#24), and oversee catechectical programs within the diocese.  Patterned after Jesus, the Good Shepherd, bishops must also govern “by their counsels, exhortations, and example, but over and above that also by the authority and sacred power which indeed they exercise exclusively for the spiritual development of their flock in truth and holiness, keeping in mind that he who is great should become as the lesser, and he who is the leader as the servant” (#27). Always mindful of his call to service like a shepherd caring for his flock, the bishop must care for the needs of the faithful entrusted to his care, extend himself even to those who no longer practice their religion, and act with charity toward those Christians of other denominations and those of other religions (Code of Canon Law, #383).

Oftentimes, in a diocese which either has a large Catholic population or covers a large territory, the bishop will be assisted by one or more auxiliaries.  An auxiliary bishop is appointed by the Holy Father at the request of the Ordinary to assist him in the governance of the diocese and take his place if he is absent or impeded (#403 & 405).   The auxiliary bishop works in harmony with the Ordinary (#407.3).

A coadjutor bishop is like an auxiliary bishop except that he has the right of succession.  When the Ordinary resigns from office or dies, the coadjutor succeeds him (#403.3).

Although ordinary, auxiliary, and coadjutor may be technical terms concerning the office of bishop, what remains most important is that a bishop is a successor of the apostles entrusted with the same office and authority our Lord entrusted to them.