Slavs
Slavs can be further grouped by religion. Orthodox Christianity is practiced by the majority of Slavs. The Orthodox Slavs include the Belarusians, Bulgarians, Macedonians, Montenegrins, Russians, Serbs, and Ukrainians and are defined by Orthodox customs and Cyrillic script as well as their cultural connection to the Byzantine Empire (Serbs also use Latin script on equal terms). Their second most common religion is Roman Catholicism. The Catholic Slavs include Croats, Czechs, Kashubs, Moravians, Poles, Silesians, Slovaks, Slovenes, and Sorbs and are defined by their Latinate influence and heritage and connection to Western Europe. There are also substantial Protestant and Lutheran minorities especially amongst the West Slavs, such as the historical Bohemian (Czech) Hussites.
Ukrainian language
Some scholars see a divergence between the language of Galicia-Volhynia and the language of Novgorod-Suzdal by the 12th century, assuming that before the 12th century, the two languages were practically indistinguishable. This point of view is, however, at variance with some historical data. In fact, several East Slavic tribes, such as Polans, Drevlyans, Severians, Dulebes (that later likely became Volhynians and Buzhans), White Croats, Tiverians and Ulichs lived on the territory of today's Ukraine long before the 12th century. Notably, some Ukrainian features were recognizable in the southern dialects of Old East Slavic as far back as the language can be documented.