Russian

Russian belongs to the East Slavic branch of the Indo-European family, closely related to Ukrainian and Belarusian, all three descended from the Old East Slavic spoken across medieval Kievan Rus before regional divergence accelerated following the Mongol invasions and later differing political trajectories under Muscovite, Lithuanian-Polish and other rule.

Russian is written in the Cyrillic script, itself developed in the ninth and tenth centuries by disciples of the Byzantine missionaries Cyril and Methodius specifically to render Slavic languages for Orthodox Christian liturgical and scriptural use, giving Russian an alphabet whose origin is directly religious rather than a later secular adaptation. Russian became the dominant literary and administrative Slavic language following Moscow's rise and the Russian Empire's expansion, absorbing vocabulary from Church Slavonic, French, and later German and English, and Soviet-era language policy spread Russian as a lingua franca across the multiethnic Soviet Union, leaving it a widely understood second language across much of the former Soviet space even after the 1991 collapse. Russian's own dialectal variation is comparatively modest next to some other major European languages, a relative uniformity linguists attribute partly to centuries of centralized Muscovite and later Soviet administration standardizing education and broadcasting across an enormous territory.

The Russian Orthodox Church's traditional liturgy is conducted not in modern Russian but in Church Slavonic, a conservative liturgical register descended from Old Church Slavonic, the language Cyril and Methodius's ninth-century mission first used to translate Byzantine Greek scripture and liturgy for Slavic-speaking converts, a distinction comparable to Latin's continued liturgical role in Catholicism after vernacular languages had otherwise diverged from it considerably.

Modern Russian-language Bible translations exist and are used for study and some non-liturgical contexts, but full vernacular liturgical reform, comparable to the Second Vatican Council's shift toward vernacular Catholic Mass, has not been formally adopted by the Russian Orthodox Church, whose leadership has generally treated Church Slavonic's archaic register as integral to liturgical solemnity and continuity rather than a barrier to comprehension requiring correction. Russian itself, rather than its liturgical Slavonic register, has become the working administrative and theological language of the modern Russian Orthodox Church's institutional life, seminaries and public commentary, including Patriarch Kirill's own extensive modern Russian-language writing and preaching.