Yat Ѣ

Yat stands thirty second and writes the vowel Slavists call yat. It carries no numeral value.

It is the letter that most rewards attention, because it never had a single agreed pronunciation. From the earliest period its value differed by region: something like a long front e in some areas, something closer to ya in others, and intermediate values elsewhere. That variation is not later corruption. It is present in the record from the beginning, and it is one of the criteria by which the recensions of Church Slavonic are distinguished.

The consequence for scribes was severe. A letter whose sound you cannot hear as distinct from another letter's sound is a letter you can only write correctly by knowing which words take it, and the confusions in the manuscripts are accordingly frequent and informative. A Slavist can often place and date a manuscript by watching where its scribe writes yat and where he slips.

In modern languages its reflexes diverge completely: Russian merged it with e, Ukrainian with i, and Bulgarian has both outcomes in different parts of the country, divided by a line running roughly north to south that has its own name in Bulgarian dialectology.

It survived in Russian orthography until 1918 and in Bulgarian until 1945, in both cases centuries after it had stopped marking anything a speaker could hear.

By the nineteenth century yat marked no distinction any Russian speaker made. It was written in a fixed list of words that had to be memorised, and it was the single most reliable way of failing a dictation. That is not a linguistic fact but a social one, and it is why the letter became political.

An orthographic rule that can only be learned, never derived, is a filter. The people who can apply it correctly are the people who had the schooling, and every argument for keeping the letter therefore carried an argument about who should be able to write. The philologists proposing to abolish it said as much, and so, in different words, did the people opposing them.

The Russian reform of 1918 removed it, along with three other letters, using proposals prepared by the Academy of Sciences before the revolution and decrees issued after it. Bulgaria removed it in 1945 under a comparable mixture of long standing scholarly argument and abrupt political will, and Bulgarian had a further complication: because the letter has two different reflexes in different parts of the country, deciding what to write instead was a choice between two regional norms, and the choice was contested for exactly that reason.

Emigre presses kept the letter for decades as a deliberate refusal, and it still appears in some publications as a marker of allegiance rather than of pronunciation. A vowel nobody could hear has been carrying political weight for well over a century, which says more about orthographies than about vowels.