Siddham O 𑖌

O is the first strengthening grade of u, standing to that vowel exactly as e stands to i, and like e it is always long in the classical language. The symmetry is not decorative. It means that a reader who meets this vowel at the front of a word is usually looking at a form built from a root containing u, and the grammar of the derivation is recoverable from the letter alone.

Historically the sound is what a and u produce when they combine, which is also why it turns up constantly at word joins. A word ending in short a followed by one beginning in u is written with this single letter, so a good proportion of the o sounds on any page are seams rather than vowels belonging to either word. Undoing the seam is part of reading, and it is the reason a Siddham text is harder to parse than its letter count suggests.

The letter carries weight far beyond its ordinary frequency because of the syllable Om, which opens and closes an enormous quantity of what was ever written in this script. The seed syllables that East Asian esoteric Buddhism took from the table are built from vowels of this kind rather than from running words, and the vowel section of the syllabary is therefore the part of it a non-reader is most likely to have seen.

A great deal of the Siddham written in Japan was never meant to be read as a text. It stands on wood and on stone, in the open, in places where the audience is the passer-by rather than the scholar. The sotoba is the clearest case: a tall thin wooden tablet, notched at the top into five sections, set up behind a grave. The notches represent the five elements and the syllables written down the board are the Siddham seed syllables that go with them, so the tablet is a stupa reduced to a plank and a letter for each of its tiers.

Stone gives the same scheme its permanent form in the gorinto, a five-tiered pagoda of cube, sphere, pyramid, half-moon and jewel, each tier carrying its syllable. Grave markers, boundary stones, memorial pillars and the small figures set at roadsides all carry Siddham of this kind, usually one syllable standing for a figure or an element rather than a sentence.

That use has a consequence worth naming. Siddham is a public script in Japan in a way it never was in India, visible in ordinary places to people who cannot read it and do not expect to. What it communicates in that setting is not the sense of a word but the fact of a dedication, which is a real function and not a failed one. The letters are doing the work of a sign rather than the work of writing.