Old East Slavic

Old East Slavic is a scholarly name for the related East Slavic varieties used in Rus’ from roughly the tenth to the fourteenth or fifteenth century, rather than a single completely uniform language. These varieties form the principal historical basis of modern Belarusian, Russian, and Ukrainian, while regional developments such as Old Novgorodian show substantial internal diversity. Written sources include chronicles such as the Primary Chronicle, legal and administrative texts, inscriptions, and the Novgorod birch-bark letters, which preserve unusually direct evidence of everyday vernacular usage from the eleventh century onward. Literary writing often combines East Slavic features with varying degrees of Church Slavonic influence. Texts were mainly written in early Cyrillic, using letters such as the yers ъ and ь, yat ѣ, and the yus letters ѧ and ѫ, whose sound values or functions later changed or disappeared in the modern languages.