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 researchers, while admitting the differences between the dialects spoken by East Slavic tribes in the 10th and 11th centuries, still consider them as "regional manifestations of a common language" (see, for instance, the article by Vasyl Nimchuk). In contrast, Ahatanhel Krymsky and Alexei Shakhmatov assumed the existence of the common spoken language of Eastern Slavs only in prehistoric times. According to their point of view, the diversification of the Old East Slavic language took place in the 8th or early 9th century.