Russian philology
Borrowings and calques from Byzantine
Greek began to enter the Old East Slavic and spoken dialects at this time, which in their turn
modified the Old Church Slavonic as well.
The Ostromir Gospels of 1056 is the second oldest East Slavic book known, one of many
medieval illuminated manuscripts preserved in the Russian National Library.
Dialectal differentiation accelerated after the breakup of Kievan Rus' in approximately 1100.
On the territories of modern Belarus and Ukraine emerged Ruthenian and in modern Russia
medieval Russian. They became distinct since the 13th century, i.e. following the division of
that land between the Grand Duchy of Lithuania, Poland and Hungary in the west and
independent Novgorod and Pskov feudal republics plus numerous small duchies (which came
to be vassals of the Tatars) in the east.
The official language in Moscow and Novgorod, and later, in the growing Muscovy, was
Church Slavonic, which evolved from Old Church Slavonic and remained the literary
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