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.
Rusyns
Most of the predecessors of the Eastern Slavic inhabitants of present-day Western Ukraine, as well as of Western Belarus, referred to themselves as Ruthenians (Rusyns) (, transliteration "Rusyny") prior to the 19th century. Many of them became active participants in the creation of the Ukrainian nation and came to call themselves Ukrainians (Ukrainian: Українці, transliteration "Ukrayintsi"). There were, however, ethnic Rusyn enclaves, which were not a part of this movement: those living on the border of the same territory or in more isolated regions, such as the people from Carpathian Ruthenia, Poleshuks, or the Rusyns of Podlaskie. In the Soviet era, Boykos, Lemkos, Hutsuls, Rusyns, Ruski, Cossacks, Pinchuks, Polishchuks, and Lytvyns were classified as Ukrainian sub-groups.