Catholicos is the English word for the head of the Armenian Church. In Armenian, the word is Katoghikos (arm: Կաթողիկոս).
Catholicos \Ca*thol"i*cos\, n. [NL. See Catholic.] (Eccl.) The spiritual head of the Armenian church, who resides at Ejmiatsin, and has ecclesiastical jurisdiction over, and consecrates the holy oil for, the Armenians of Russia, Turkey, and Persia, including the Patriarchs of Constantinople, Jerusalem, and Sis.
Note: The Patriarch of Constantinople is the civil head of the Armenians in Turkey.
Source: Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
Among the Armenians also catholicos was originally a simple title for the principal bishop of the country; he was subordinate to the See of Caesarea in Cappadocia. The bishops of Albania and Georgia, although dependent on the Catholicos of Armenia bore the same title. Under King Pap and the Catholicos lousik Armenia asserted its independence of Caesarea. In the fifth century the Armenians adopted Monophysitism and anathematized the Council of Chalcedon, 491. Many of the catholicoi, however, especially after the Crusades, professed the orthodox Catholic Faith. The see of the Armenian catholicos, originally Achtichat, has varied considerably. Besides many schisms have taken place, and today there are no less than five Armenian catholicoi. One of them, the successor of the old catholicos, is at Sis in Cilicia, with jurisdiction over the Turkish provinces of Asia. His power in ecclesiastical matters, supreme in theory, is considerably curtailed in practice by the appointment of a catholicoi with additional powers in Constantinople. Since 1113 there is also an Armenian catholicos at Aghtamar with jurisdiction over the island of that name and the villages surrounding Lake Van. Another catholicos resides in Jerusalem, but with greatly reduced powers. In 1441 another schism occurred, and a catholicos was elected in Etchmiadzin in Greater Armenia. Today he bears the title of "Supreme Patriarch and Catholicos of all Armenians" and at least theoretically, is considered the principal catholicos by all non-Catholic Armanians. Since 1740 there has also been a Catholic catholicos in Constantinople with the title of Patriarch of Cilicia. He is recognized by the Porte as having jurisdiction over all Catholic Armenians in the Turkish possessions. (See ARMENIA; CONSTANTINOPLE.)