A report on Yat

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 "Yat border" running approximately from Nikopol on the Danube to Thessaloniki on the Aegean Sea is the main isogloss separating the Eastern South Slavic dialects into Eastern and Western.

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

Jouko Lindstedt has assumed that the dividing line between Macedonian and Bulgarian may be in fact the Yat border, which goes through the modern region of Macedonia along the Velingrad – Petrich – Thessaloniki line.

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 primary subdivisions of Shtokavian are based on two principles: one is whether the subdialect is Old-Shtokavian or Neo-Shtokavian, and different accents according to the way the old Slavic phoneme jat has changed.

The modern reflexes of the long Common Slavic vowel jat, usually transcribed *ě, vary by location as /i/, /e/, and /ije/ or /je/.

Ѣ ѣ : Cyrillic letter Yat

According to the reflex of the Common Slavic phoneme yat */ě/, there are four varieties:

Russian orthography was made simpler and easier by unifying several adjectival and pronominal inflections, conflating the letter ѣ (Yat) with е, ѳ with ф, and і (depending on the context of Moscovian pronunciation) and ѵ with и.