What title is held by the Head of both the Russian and Greek Orthodox churches?
Patriarch (Christian churches) Patriarch and Patriarchate Patriarchēs Patriarchs of the One Holy Catholic and Apostolic Church Patriarch of the West Patriarch Eastern patriarchs Patriarchs PATRIARCH
patriarch and patriarchate eastern patriarchs patriarchēs patriarch christian churches patriarch patriarchs patriarch of west patriarchs of one holy catholic and apostolic church
patriarch
WikipediaEntity
PATRIARCH