Eastern Orthodox Church

Part of a series on the Eastern Christianity
History
Byzantine Empire Crusades Ecumenical council Christianization of Bulgaria Christianization of Kievan Rus' East-West Schism
by regions
Asian - Copts Eastern Orthodox - Georgian - Ukrainian
Traditions
Assyrian Church of the East Eastern Orthodox Church Eastern Catholic Churches Oriental Orthodoxy Syriac Christianity
Liturgy and Worship
Sign of the cross Divine Liturgy Iconography Asceticism Omophorion
Theology
Hesychasm - Icon Apophaticism - Filioque clause Miaphysitism - Monophysitism Nestorianism - Theosis - Theoria Phronema - Philokalia Praxis - Theotokos Hypostasis - Ousia Essence - Energies distinction Metousiosis

The Eastern Orthodox Church is the second largest single Christian communion in the world with an estimated 300 million members worldwide.[1] It is considered by its adherents to be the One, Holy, Catholic and Apostolic Church established by Jesus Christ and his Apostles nearly 2000 years ago. The Church is composed of numerous self-governing ecclessial bodies, each geographically and nationally distinct but theologically and sacramentally unified. Each self-governing (or autocephalous) body is shepherded by a Synod of independent bishops whose duty is, among other things, to preserve and teach the Apostolic and patristic traditions and related Church practices. All Orthodox bishops trace their lineage back to one of the twelve Apostles through the process of Apostolic Succession.

Eastern Orthodoxy traces its history back to the Hellenized eastern portion of the Roman Empire, especially Constantinople or New Rome (now Istanbul). It shares the first ecumenical councils, concerning the Trinity and the Nicene Creed, with nearly all other Christians.

After the Western Roman Empire fell, East and West slowly grew more separate. Meanwhile, internal schisms and the advance of Islam reduced Eastern Orthodox territory, but the faith spread to the Slavs to the north (including the Russians). Eastern Orthodoxy and Roman Catholicism split in 1054 over theological issues concerning Western additions to the creed (the filioque clause) as well as the issue of Roman primacy. Later in 1204 Constantinople was sacked by crusaders enlarging the rift between the two. Reunification was attempted during two councils but they were rejected by the Eastern Orthodox people, being considered "robber councils". After Constantinople fell to the Ottoman Turks in 1453, the Russian Orthodox Church became more powerful.

Efforts are under way to heal the division that since the Council of Chalcedon (451) exists between them and Oriental Orthodoxy in connection with the proper way to speak of the two natures (one human and one divine) of Christ. They use the Nicene Creed as endorsed at the First Council of Constantinople (381), and reject the Western addition to it of "Filioque", and the many additions used by the Armenian Apostolic Church in the East. They celebrate the same sacraments (called sacred mysteries) as in the other ancient Christian Churches, but have some differences in theology and many differences in practice.

They teach the doctrine of theosis (deification), by which Christ makes it possible to partake of the divine, a teaching less prominent in the Western Church.[5] Their Bible is close to that of the Roman Catholic Church: it includes the Deuterocanonical Books, which are generally rejected by Protestants, and a few texts that are not in the Western canon. Eastern Orthodox icons also reflect an ancient opposition to statuary. Most Eastern Orthodox Churches are members of the World Council of Churches,which includes most Protestants, but not Roman Catholics.