yat

A vowel letter of the Cyrillic and Glagolitic alphabet (Cyrillic capital Ѣ, Cyrillic small ѣ, Glagolitic ⱑ), no longer in current use

The Late Proto-Slavic (Common Slavic) vowel that was represented by this letter, usually transcribed as /ě/. This vowel underwent various alterations in the later Slavic dialects and is no longer distinguished (except in Ijekavian).