西スラヴ語群
In Old Church Slavonic, the yer was used to indicate the so-called "reduced vowel": ъ = , ь = in the conventional transcription. They stemmed from the Proto-Balto-Slavic short and (compare Latin angulus and Old Church Slavonic ѫгълъ, ""). In all West Slavic languages, the yer either disappeared or changed to in strong positions, and in South Slavic languages, the strong yer reflexes differ widely, according to dialect.