Originally, a bishop was an overseer as his name in Greek implies. Bishops now form the leadership in the the Eastern Orthodox Church. A bishop is chosen from among the ranks of the priests but only an unmarried priest may become a bishop.
A bishop has jurisdiction over a bishopric (diocese or archdiocese) - an area with several parishes and local churches. Ultimately, all authority within a diocese is derived from a bishop without whose authorisation no service may be conducted in an Orthodox church.
In the Greek tradition, the bishop sits or stands at the bishop's throne on the south side of the church, on the solea. The back of the chair of this throne has an icon depicting Christ the King, and the bishop will first venerate this icon before occupying the throne.
At times during the services, the bishop blesses the faithful with two candlesticks, one with two candles called dikiri and the other with three called trikiri, the first symbolizing the two natures of Christ, the other symbolizing the three persons of the Holy Trinity.
Liturgically, the bishop is dressed similar to a priest but also wears the omophorion - a wide band of cloth worn about the shoulders. He carries a staff called a crosier and wears an elaborate crown called a mitre.
Though all bishops are deemed equal, there are distinctions among them.
- A Patriarch is head of one of the five major sees (Constantinople, Alexandria, Jerusalem, Antioch and Rome) or the nation-churches that came into existance later (Russia, Romania, Bulgaria, etc.)
- An Archbishop is head over a large see with several dioceses within it e.g. the Archbishop of Greece, the Archbishop of America, etc.
- A Metropolitan is head over an important diocese e.g. Attica, Patra, Piraeus, Thessaloniki, etc.