Old East Slavic

Old East Slavic, also referred to as Old Russian and Rusian (sic, with one ‘s’, from Rus’), was a language used in the 10th–15th centuries by East Slavs in Kievan Rus' and states which evolved after the collapse of Kievan Rus'. Dialects of it were spoken, though not exclusively, in the area today occupied by Belarus, central and northern Ukraine, parts of western Russia, and several eastern voivodships of Poland.