Om
The Imperishable Syllable
Held to be the sound of ultimate reality itself — one syllable, and continuous with the self who says it.
Om, written ॐ, is a Devanagari ligature of a and u with the chandrabindu that carries the closing nasal. The syllable is ancient: the Chandogya Upanishad, of perhaps the seventh or sixth century BCE, opens by enjoining meditation on it as the udgitha, the chant. The Mandukya Upanishad — twelve verses, usually dated near the turn of the Common Era — is given wholly to it, assigning A, U and M to waking, dream and dreamless sleep, with a soundless fourth for turiya, the state beyond. Reading the drawn curves, crescent and dot as those states is a later convention. Jainism takes the syllable as the initials of the five Parameshthis; Sanskrit-tradition Buddhism uses it, though Tibetan writes ༀ, and Sikhism's Ik Onkar is a different sign.
Light
Signifies the whole of reality gathered into a single sound, and the continuity of that reality with the self. Spoken to open and close recitation, study and worship, it serves as concentration and as assent.
Shadow
Now commonly detached from its meaning and used as a serenity motif, printed on footwear and floor mats over Hindu objection. Older dharmashastra reserved the pranava, the syllable itself, to the twice-born, making it a marker of who might study the Veda.
