Avestan Aao and the Eight Vowel Pairs

The long rounded open vowel completes a pair whose two members differ in nothing but duration. Preserving that difference on the page is only worth the trouble if somebody is expected to reproduce it aloud. The gap between the words and the writing is the central fact about this alphabet, and it runs in both directions. The Avesta is far older than the script, and every surviving manuscript is far younger, so the script sits between two long stretches of transmission and belongs wholly to neither.

The Zoroastrian communities that carried these manuscripts, in Iran and in western India, are small, and the copying was sustained by priestly families rather than by any large institution. That the texts survive at all is a consequence of that continuity. In the digital record the letter is encoded at U+10B03 AVESTAN LETTER AAO. 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.