A report on Bulgarian language, Old Church Slavonic, South Slavic languages and Yat

Bulgarian (, ; български, ) is a South Slavic language spoken in Southeastern Europe, primarily in Bulgaria.

The first South Slavic language to be written (also the first attested Slavic language) was the variety of the Eastern South Slavic spoken in Thessaloniki, now called Old Church Slavonic, in the ninth century.

Bulgarian – (ISO 639-1 code: bg; ISO 639-2 code: bul; SIL code: bul; Linguasphere: 53-AAA-hb)

One explanation is that the dialect of Thessaloniki (on which the Old Church Slavonic literary language was based), and other South Slavic dialects shifted from to independently from the Northern and Western branches.

The term Old Bulgarian (старобългарски, Altbulgarisch) is the only designation used by Bulgarian-language writers.

Old Bulgarian (9th to 11th centuries, also referred to as "Old Church Slavonic") – a literary norm of the early southern dialect of the Proto-Slavic language from which Bulgarian evolved. Saints Cyril and Methodius and their disciples used this norm when translating the Bible and other liturgical literature from Greek into Slavic.

бял / бели in Bulgarian (бел / бели in Western dialects)

Old Church Slavonic spread to other South-Eastern, Central, and Eastern European Slavic territories, most notably Croatia, Serbia, Bohemia, Lesser Poland, and principalities of the Kievan Rus' – while retaining characteristically South Slavic linguistic features.

However, modern Serbian linguists such as Pavle Ivic have accepted that the main isoglosses bundle dividing Eastern and Western South Slavic runs from the mouth of the Timok river alongside Osogovo mountain and Sar Mountain.

The pronunciation of yat (ѣ/ě) differed by area. In Bulgaria it was a relatively open vowel, commonly reconstructed as, but further north its pronunciation was more closed and it eventually became a diphthong (e.g. in modern standard Bosnian, Croatian and Montenegrin, or modern standard Serbian spoken in Bosnia and Herzegovina, as well as in Czech — the source of the grapheme ě) or even in many areas (e.g. in Chakavian Croatian, Shtokavian Ikavian Croatian and Bosnian dialects or Ukrainian) or (modern standard Serbian spoken in Serbia).

The alphabet of Marin Drinov was used until the orthographic reform of 1945, when the letters yat (uppercase Ѣ, lowercase ѣ) and yus (uppercase Ѫ, lowercase ѫ) were removed from its alphabet, reducing the number of letters to 30.

The Chakavian reflex of proto-Slavic yat is i or sometimes e (rarely as (i)je), or mixed (Ekavian–Ikavian).