This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Brahmi Letters gathers fifty one letters of the ancestral Indic script behind the writing systems of the Indian subcontinent and much of Southeast Asia, its evidence drawn chiefly from the Ashokan edicts and the Prakrit and Sanskrit inscriptions that followed them.
Brahmi is an abugida: every consonant sign is read with an inherent short vowel, A, unless a vowel mark is added or the virama cancels it, so a sign such as Ka is a full syllable rather than a bare consonant. Its vowels are organised in pairs of short and long, such as A and Aa, ending in four compound vowels, Ai and Au among them, built as strengthened grades of the simple vowels beneath them. Its consonants form a table of five classes running from the back of the mouth to the front, velar, palatal, retroflex, dental and labial, each class carrying the same four way pattern of voice and aspiration before its own nasal, letters such as Ba, Bha, Ca, Cha, Da, Dda, Ddha and Dha among them, an analysis by feature rather than a list of unrelated shapes, economical enough that a table of nearly fifty letters could be held in memory and recited in fixed sequence.
The script's descendants across the subcontinent changed some letters only a little, so comparing a letter's shape across them is the ordinary method of Indian palaeography, the basis for dating an inscription that carries no date of its own. Reading a Brahmi text also means reading a language changing under it: the Prakrit of the edicts already shows sounds merging and clusters simplifying that classical Sanskrit had kept apart.