The Eastern Orthodox Church, officially the Orthodox Catholic Church, is the second -largest Christian church, with over 250 million members. As one of the oldest religious institutions in the world, the Orthodox Church has played a prominent role in the history and culture of Eastern and Southeastern Europe, the Caucasus, and the Near East. It operates as a communion of autocephalous churches, each governed by its bishops, called a Holy Synod. The church has no central doctrinal or governance authority analogous to the Roman Catholic pope, but the Ecumenical Patriarch of Constantinople is recognised by all as primus inter pares ("first among equals") of the bishops.
Eastern Orthodox theology is based on the Nicene Creed, and the church teaches that it is the One, Holy, Catholic and Apostolic church established by Jesus Christ in his Great Commission, and that its bishops are the successors of Christ 's apostles. It maintains that it practices the original Christian faith, passed down by sacred tradition. Its patriarchates, reminiscent of the pentarchy, and autocephalous and autonomous churches reflect a variety of hierarchical organisation. Of its innumerable Sacred Mysteries, it recognises seven " major sacraments," of which the Eucharist is the principal one, celebrated liturgically in synaxis. The church teaches that through consecration invoked by a priest the sacrificial bread and wine become the body and blood of Christ. The Virgin Mary is venerated in the Eastern Orthodox Church as the Mother of God, honoured in devotions.
