The Last Vowel, and the Turn to the Consonants

Au is the second strengthening grade of the back series, standing to o as ai stands to e, and it is produced by the same set of suffixes that call for vrddhi in the front series. It is always long and always heavy in metre. Like ai it appears most often at the head of a word, because the strengthening applies to the first syllable of the stem, so the independent letter is the form a reader usually meets rather than the attached mark.

With this letter the vowel section of the order closes and the consonants begin. That transition is the main structural joint in the Brahmi alphabet, and it is the point at which a learner moves from a series arranged by quantity and grade to a series arranged by place of articulation. The consonants open at the back of the mouth with the velars and move forward class by class to the lips, so the two halves of the order are built on different principles and the join between them is where the design shows most plainly. In the Prakrit of the Ashokan edicts the sound had largely fallen together with o, so the letter is written far less often in the earliest inscriptions than the completeness of the vowel table would suggest.

For a reader of inscriptions the practical point is that the last four vowels are met chiefly at the beginnings of words, where the independent letters have to be written out in full. That makes them disproportionately visible on stone relative to how often the sounds occur, since the vowels inside words are carried by marks rather than by letters. A count of independent vowel signs in an inscription therefore says more about where words begin than about which vowels the language uses.