Slavs
Slavs are the largest ethno-linguistic group in Europe. Present-day Slavic people are classified into East Slavs (chiefly Belarusians, Russians, Rusyns, and Ukrainians), West Slavs (chiefly Czechs, Kashubs, Moravians, Poles, Silesians, Slovaks and Sorbs), and South Slavs (chiefly Bosniaks, Bulgarians, Croats, Macedonians, Gorani, Pomaks, Montenegrins, Serbs and Slovenes).
Ukrainian language
During the Khazar period, the territory of Ukraine was settled by Iranian (post-Scythian), Turkic (post-Hunnic, proto-Bulgarian), and Uralic (proto-Hungarian) tribes and Slavic tribes. Finally, the Varangian ruler of Novgorod, called Oleg, seized Kiev (Kyiv) and established the political entity of Kievan Rus'. Some theorists see an early Ukrainian stage in language development here; others term this era Old East Slavic or Old Ruthenian/Rus'ian. Russian theorists tend to amalgamate Rus' to the modern nation of Russia, and call this linguistic era Old Russian. Some hold that linguistic unity over Rus' was not present, but tribal diversity in language was.