Yat border

Bulgarian

In Bulgarian the different reflexes of the yat form the so-called Yat border (ятова граница), running approximately from Nikopol on the Danube to Solun (Thessaloniki) on the Aegean Sea. West of that isogloss, old yat is always realized as /ɛ/. East of it, the reflexes of yat prototypically alternate between /ja/ or /ʲa/ (in stressed syllables when not followed by a front vowel) and /ɛ/ (in all other cases). The division of the dialects of the Eastern South Slavic into western and eastern subgroup running along the yat border is the most important dividing isogloss there. The open articulation of yat (as /æ/ or ja) and the reflexes of Proto-Slavic *tj/*ktĭ/*gtĭ and *dj as ⟨щ⟩ (ʃt) and ⟨жд⟩ (ʒd) have traditionally been considered the two most distinctive phonetic features of Old Bulgarian. Based on