Ruthenian

Ruthenian (see also other names) was a written language used from the 14th to the 18th centuries within the East Slavic-speaking regions of the Grand Duchy of Lithuania and later the Polish-Lithuanian Commonwealth. Literary Ruthenian is considered to be a historical precursor to the modern Belarusian and Ukrainian languages (occasionally also to Rusyn), although neither standard language directly continues the Ruthenian written tradition.

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).