Avestan Uu and the Close of the Vowel Section

With this letter the vowel section closes, sixteen signs deep. No script in the region at the time carried a vowel inventory of that size, and none of its neighbours had the same reason to want one. Book Pahlavi is the hand behind these letterforms, and the relationship between the two is one of correction. In that writing a number of originally distinct sounds had come to share a single shape, so reading it depends on recognising words rather than on assembling them from letters.

The Avestan alphabet takes the same pen strokes and separates what had merged. Because the surviving copies are late, the evidence for what any individual letter did rests on the consistency of the manuscript tradition rather than on early witnesses. Where the copies agree, editors follow them; where they do not, the disagreement is recorded rather than settled by preference. In the digital record the letter is encoded at U+10B0F AVESTAN LETTER UU. The whole Avestan block lies above the Basic Multilingual Plane, so each character needs a surrogate pair in the encodings that use them, and a font carrying the script is required before anything appears on a screen at all. For the community the value of a script that writes every sound is continuity. It makes it possible to check a recitation against a page rather than against another reciter's memory, which is what the alphabet was for and what it still does.