Old Ruthenian language may refer to:
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Old East Slavic, a language used in the 10th to 14th centuries by East Slavs in Kyivan Rus', ancestor of Russian and Ruthenian (ancestor of Belarusian, Rusyn, and Ukrainian)
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Ruthenian language, a language used in the 15th to 18th centuries in the Grand Duchy of Lithuania and the Cossack state, ancestor of Belarusian, Rusyn, and Ukrainian
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