The Eastern Orthodox Church is a Christian body that views itself as the historical continuation of the original Christian community established by Jesus and the Twelve Apostles, preserving the traditions of the early church unchanged, accepting the canonicity of the first seven ecumenical councils held between the 4th and the 8th centuries, and maintaining the unbroken link between its clergy and the Apostles by means of Apostolic Succession.
The Orthodox Church is organized into numerous autocephalous "jurisdictions" or "particular churches", the largest single one of which in terms of membership is the Russian Orthodox Church. Other major jurisdictions include the Greek, Serbian, Bulgarian and Romanian churches. Each of these has its own synod of bishops to act as governors. The Orthodox Church holds the Patriarch of Constantinople to be the first among equals among the Orthodox episcopacy.
Based on the numbers of adherents, Eastern Orthodoxy is the second largest Christian communion in the world after the Roman Catholic Church, and the third largest grouping if Protestantism is counted as a whole. Estimates of the number of Eastern Orthodox Christians worldwide range from 50 million to 350 million, with 220 million being one of the most commonly cited figures.