This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Avestan Letters gathers the fifty four letters of din dabireh, the religion writing, the script built in Sasanian Iran centuries after the Avesta was composed, to hold a text priests had until then carried whole in memory.
The alphabet runs sixteen vowels before thirty eight consonants, a larger inventory than the neighbouring scripts of its region and period, because it was designed to fix one recitation rather than to conduct ordinary business. Its vowels are written as full letters standing in the line rather than as marks hung on a consonant, the clearest break the script makes from the Book Pahlavi hand its letterforms are built on, a hand in which several distinct sounds had come to share one shape; the Avestan alphabet takes that ambiguity apart, arranging vowels in short and long pairs, such as A and Aa, and giving even a rare nasalised vowel or a reduced schwa its own dedicated sign. The letters are ordered by phonetic analysis, vowels first, then consonants by place of articulation moving from the back of the mouth toward the front, not by any sequence inherited from the Aramaic tradition that supplied the letterforms themselves.
No Avestan manuscript survives from earlier than the thirteenth century, so every copy in existence is far younger than the script, and the script is far younger than the words it carries. Zoroastrianism remains a small living religion, and the Avesta its liturgy, recited in worship today, so the alphabet's exactness is not an antiquarian curiosity: it records sounds a priest is still expected to produce.