Nature and significance
Eastern Orthodoxy is the large body of Christians who follow the faith and practices that were defined by the first seven ecumenical councils. The word orthodox (“right believing”) has traditionally been used in the Greek-speaking Christian world to designate communities or individuals who preserved the true faith (as defined by those councils), as opposed to those who were declared heretical. The official designation of the church in Eastern Orthodox liturgical or canonical texts is “the Orthodox Catholic Church.” Because of the historical links of Eastern Orthodoxy with the Eastern Roman Empire and Byzantium (Constantinople), however, in English usage it is referred to as the “Eastern” or “Greek Orthodox” Church. These terms are sometimes misleading, especially when applied to Russian or Slavic churches and to the Orthodox communities in western Europe and America.
It should also be noted that the Eastern Orthodox Church constitutes a separate tradition from the churches of the so-called Oriental Orthodox Communion, now including the Armenian Apostolic Church, the Ethiopian Tewahedo Orthodox Church, the Eritrean Tewahedo Orthodox Church, the Coptic Orthodox Church, the Syriac Orthodox Partriarchate of Antioch and All the East, and the Malankara Orthodox Church of India. From the time of the Council of Chalcedon in 451 to the late 20th century, the Oriental Orthodox churches were out of communion with the Roman Catholic Church and later the Eastern Orthodox Church because of a perceived difference in doctrine regarding the divine and human natures of Jesus. This changed in the 1950s, when both churches independently began dialogue with the Oriental Orthodox churches and resolved many of the ancient Christological disputes.