function are known as diocesan ordinaries, because they have what canon law calls ordinary (i.e. not delegated) authority for a diocese. These bishops may be known as hierarchs in the Eastern Catholic Churches. Other bishops may be appointed to assist ordinaries (auxiliary bishops and coadjutor bishops) or to carry out a function in a broader field of service to the Church, such as appointments as papal nuncios or as officials in the Roman Curia. Bishops of a country or region may form an episcopal conference and meet periodically to discuss current problems. Decisions in certain fields, notably liturgy, fall within the exclusive competence of these conferences. The decisions of the conferences are binding on the individual bishops only if agreed to by at least two-thirds of the membership and confirmed by the Holy See. Bishops are normally ordained to the episcopate by at least three other bishops, though for validity only one is needed and a mandatum from the Holy See is required. Ordination to the episcopate is considered the completion of the sacrament of Holy Orders; even when a bishop retires from his active service, he remains a bishop, since the ontological effect of Holy Orders is permanent. On the other hand, titles such as archbishop or patriarch imply no ontological alteration, and existing bishops who rise to those offices do not require further ordination. Sacramentally, all bishops are equal. According to jurisdiction, office, and privileges, however, various ranks are distinguished, as indicated below. All bishops are "vicars of Christ". Pope (Bishop of Rome) The pope is the bishop of Rome. He is also, by virtue of that office: Offices and titles "Pope" is a pronominal honorific, not an office or a title, meaning "Father" (the common honorific for all clergy). The honorific "pope" was from the early 3rd century used for any bishop in the West, and is known in Greek as far back as Homer's Odyssey (6:57). In the East, "pope" is still a common form of address for clergy in the Bulgarian Orthodox Church and the Russian Orthodox Church, and is the style of the bishop of Alexandria. Pope Marcellinus (died 304) is the first Bishop of Rome shown in sources to have had the title "pope" used of him. From the 6th century, the imperial chancery of Constantinople normally reserved this designation for the Bishop of Rome. From the early 6th century, it began to