Ruthenian language

Ruthenian (руска(ѧ) мова, рус(ь)кй ѧзыкъ; see also other names) is an exonymic linguonym for a closely related group of East Slavic linguistic varieties, particularly those spoken from the 15th to 18th centuries in the Grand Duchy of Lithuania and in East Slavic regions of the Polish–Lithuanian Commonwealth. Regional distribution of those varieties, both in their literary and vernacular forms, corresponded approximately to the territories of the modern states of Belarus and Ukraine. By the end of the 18th century, they gradually diverged into regional variants, which subsequently developed into the modern Belarusian, Ukrainian, and Rusyn languages.

In the Austrian and Austro-Hungarian empires, the same term (German: ruthenische Sprache; Hungarian: Rutén nyelv) was employed continuously (up to 1918) as an official exonym for the entire East Slavic linguistic body within its borders.

Several linguistic issues are debated among linguists: various questions related to classification of literary and vernacular varieties of this language; issues related to meanings and proper uses of various endonymic (native) and exonymic (foreign) glottonyms (names of languages and linguistic varieties); questions on its relation to modern East Slavic languages, and its relation to Old East Slavic (the colloquial language used in Kievan Rus' in the 10th through 13th centuries).