Big Yus Ⱘ

Big yus writes the back nasal vowel, the second member of the pair of nasal vowels that Old Church Slavonic inherited, and it carries no numeral value.

The vowel it records was lost across almost all of the Slavic world. Where it stood, the modern languages have an ordinary oral vowel, arrived at by denasalisation at various dates in various places, and only Polish retains nasal vowels of its own. A word written with this letter in an early manuscript can therefore be traced to a nasal vowel in the parent language on the strength of the spelling alone, which is the sort of leverage that makes an early orthography worth studying in its own right.

The letter is common in the canon, because the vowel it wrote occurred in frequent endings, so its forms are well attested in both hands of the script.

Its name is opaque and the reference literature records it without an etymology. The atlas treats that, as it treats the rest of the names at this end of the alphabet, as a gap in the record rather than as an invitation to supply a reading, and it carries an open question stating what a study of the whole set would have to establish.

No number attaches to it in Glagolitic. The counted series in this script stops at the second letter for the vowel o, and everything after that, including both nasal vowels and all four nasal signs, stands outside the arithmetic. Cyrillic leaves the same letter unnumbered for its own reason, that Greek had nothing in the slot to inherit from.

The disappearance of the nasal vowels is one of the largest changes in the history of Slavic, and the two yus letters are how it is tracked. Because they were written before the change and continued to be written for a time afterwards, the manuscripts record the process in progress rather than only its result.

The signs of that are visible in the way scribes used the letters. Early texts keep the two nasal vowels apart and keep both apart from the oral vowels they would eventually become. Later texts begin to confuse them, first in particular positions and then generally, and eventually a scribe writes a yus where the older orthography had an oral vowel, which shows the letter has become a spelling convention with no sound behind it. Each stage can be dated approximately and located approximately, and the pattern differs between regions.

That is why the yus letters are among the first things a Slavist looks at in an unplaced manuscript. They are a clock that was running while the books were being copied. The letter itself is not the change and does not cause it; it is a fixed point against which the change can be measured, which is what an old orthography always is once the language has moved past it.