古教会斯拉夫语(Old Church Slavic language)
主要以帖撒罗尼迦（Thessalonica）周围地区的马其顿诸方言（南部斯拉夫诸方言）为基础的斯拉夫语，9世纪时传教士圣西里尔与圣美多迪乌斯曾用这种语言布道并译写《圣经》。古教会斯拉夫语是最早的斯拉夫文学语言，采用格拉哥里字母（Glagolitic alphabet）和西里尔字母书写。在欧洲中世纪时期，这种语言始终是信奉东正教的斯拉夫人的宗教语言和文学语言。西元12世纪以後，古教会斯拉夫语以各种地方变体出现，统称为教会斯拉夫语，作为一种教会仪式语言沿用至今。19世纪以前，塞尔维亚和保加利亚人都使用教会斯拉夫语作为书面语言，对现代斯拉夫诸语言的发展曾有重大影响，对俄罗斯文学语言影响更大。
English version：
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 Slavic (or Old Church Slavonic) documents, all translations from Christian ecclesiastical texts, resulted from the mission to the Moravian Slavs of Sts. Cyril and Methodius, though all but one of the surviving manuscripts were actually copied in South Slavic-speaking areas. Beginning already 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 Slavic. Church Slavic 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. Old Church Slavic and Church Slavic are more archaic than any living Slavic language in completely retaining both the original Slavic verbal system and the full set of seven nominal cases and three numbers.