or Old Church Slavic language
Oldest attested Slavic language , known from a small corpus of 10th-or 11th-century manuscripts, most written in the Glagolitic alphabet (see Cyrillic alphabet ).
The Old Church Slavonic documents, all translations from Christian ecclesiastical texts, resulted from the mission to the Moravian Slavs of Saints Cyril and Methodius , though all but one of the surviving manuscripts were actually copied in South Slavic-speaking areas. Beginning in the 11th century, the influence of the vernacular languages in cultural focal areas (Serbia, Bulgaria-Macedonia, Ukraine, and Russia) led to regional variations in Church Slavonic. It remained the literary language of Eastern Orthodoxy in South Slavic and East Slavic lands into modern times and is still the liturgical language of Slavic Orthodoxy and the Slavic Eastern rite church .