The Eastern Orthodox Church, officially the Orthodox Catholic Church, is the second largest Christian temple, with approximately 220 million baptized members, it acts as a community with autocephalous churches, each regulated by bishops in local cathedrals. Approximately half of the Orthodox Christians live in Russia. The Church has no central doctrinal or governmental authority similar to that of the bishop of Rome, but the Ecumenical Patriarch of Constantinople is recognized by all as primus inter pares ("first among equals") bishops. As one of the oldest surviving religious institutions in the world, the Eastern Orthodox Church plays an outstanding role in the history and culture of Eastern and Southeast Europe, the Caucasus and the Middle East.
Eastern Orthodox theology is based on a sacred tradition that includes the dogmatic decrees of the Seven Ecumenical Councils, the Scriptures and the teachings of the Church Fathers. The Church teaches that it is one, holy, cathedral and apostolic Church established by Jesus Christ in his Great Commission , and that its bishops are successors from Christ to the apostles. He claims that he practices the original Christian faith transmitted by the Holy Tradition. His patriarchates, reminiscent of the Pentaarchy and other autocephalous and autonomous churches, reflect different hierarchical organizations. He recognizes seven major sacraments, of which the Eucharist is the main one, performed liturgically in synax. The Church teaches that through sanctification, to which the priest calls, the sacrificial bread and wine becomes the body and blood of Christ. The Virgin Mary is revered in the Orthodox Church as the Blessed Virgin Mary, and is honored in piety.
The Eastern Orthodox Church shared with the Roman Catholic Church in the state church of Rome until the East-West split in 1054, challenging in particular the authority of the Pope. Before Ephesus in 431 AD. The Church of the East also shares in this communion, as the Eastern Orthodox churches did before Chalcedon in 451, all the branches primarily over the differences in Christology.
Most Orthodox Christians live mainly in Southeast and Eastern Europe, in Cyprus, Georgia and other communities in the Caucasus region, and communities in Siberia reach the Russian Far East. There are also small communities in the former Byzantine regions in Africa, the Eastern Mediterranean and the Middle East, where it is decreasing due to - forced migration from - increased religious persecution in recent years. There are also many other parts of the world formed through diaspora, conversion and missionary activity.