Old Church SlavonicOld Church Slavonic (or simply Church Slavonic, Old Slavonic, or Old Slavic) is the first literary and liturgical Slavic language developed by the 9th-century missionaries Saints Cyril and Methodius, most important in Eastern Orthodoxy and its spread into the countries of the Slavic peoples. (See also liturgical language.)
Cyril and Methodius hailed from Thessaloniki and based Old Church Slavonic on the Slavic dialect of the Thessaloniki region. Some scholars (mostly Bulgarian) regard Old Church Slavonic as an Old Bulgarian dialect. It has many South Slavic word forms.
Church Slavonic maintained a prestige status, particularly in Russia, for many centuries -- it had among Slavs in the East a status analogous to that of the Latin language in western Europe, but had the advantage of being less divergent from the vernacular tongues of average parishioners. Some Eastern Orthodox churches, such as the Russian and Serbian churches, still use Church Slavonic in their services and chants. Additionally, several Eastern Rite Catholic churches use Church Slavonic.