https://en.wikipedia.org/wiki/Cyrillic_alphabets
Slavic languages. Cyrillic alphabets used by Slavic languages can be divided into two categories: . East South Slavic languages and East Slavic languages, such as Bulgarian and Russian, share common features such as Й, ь, and я.; West South Slavic languages, such as Serbian, share common features such as Ј and љ.; East Slavic Russian