Old East Slavic was a language used by the East Slavs from the 7th or 8th century to the 13th or 14th century, until it diverged into the Russian and Ruthenian languages. Ruthenian eventually evolved into the Belarusian, Rusyn, and Ukrainian languages.

Russian is an East Slavic language, spoken primarily in Russia. It is the native language of the Russians and belongs to the Indo-European language family. It is one of four living East Slavic languages, and is also a part of the larger Balto-Slavic languages. It was the de facto and de jure official language of the former Soviet Union. Russian has remained an official language in independent Russia, Belarus, Kazakhstan, Kyrgyzstan, and Tajikistan, and is still commonly used as a lingua franca in Ukraine, Moldova, the Caucasus, Central Asia, and to a lesser extent in the Baltic states and Israel.