Om

Om, also written Aum and rendered in Devanagari as a single ligature, is the most concentrated sacred sound of the Indian traditions. The Mandukya Upanishad, one of the shortest of the principal Upanishads, is devoted entirely to it, analysing the syllable into three morae, A, U and M, identified with the waking, dream and deep-sleep states, and a silent fourth (turiya) beyond them, identified with the absolute. The Chandogya Upanishad opens by calling the udgitha, the sung Om of the Samaveda liturgy, the essence of all essences. Om thus stands at the junction of ritual chant and metaphysics: at once a practical liturgical vocable that opens and closes Vedic recitation and mantra, and a symbol of ultimate reality (Brahman, identified with the Atman or self).

The Mandukya Upanishad's analysis of Om into three sounds and a silent fourth became one of the most commented-upon short texts in the Vedantic tradition, most influentially through Gaudapada's Karika, a verse commentary of early but uncertain date reading the syllable's structure as a map of consciousness, waking, dreaming and dreamless sleep understood as states the seeker passes through toward the silence beyond sound that is turiya, pure awareness. Because the Upanishad treats Om as identical with Brahman rather than merely symbolic of it, later Vedanta philosophers built entire systems on the claim that meditating on the syllable is direct engagement with ultimate reality, a stronger claim than most traditions make for their own sacred words. In Tibetan Buddhist mantra Om is paired with Ah and Hum to mark body, speech and mind at the head of longer formulas such as Om mani padme hum, keeping Om's Vedic role as an opening, consecrating sound while attaching it to an entirely different doctrinal system.

Om is not confined to one religion. In Hinduism it prefaces most mantras and is treated as the sound-form of Brahman. Buddhism carries it into mantra, most famously Om mani padme hum, and into Vajrayana ritual, where Om, Ah and Hum mark body, speech and mind. Jainism reads Om as a compression of the Panca-Namaskara, the fivefold homage, formed from the initials of its five honoured beings. Sikh scripture opens with Ik Onkar, in which onkar is cognate, though Sikh theology reads it strictly as the one God and keeps its distance from pluralist metaphysics. The visual symbol's worldwide circulation on jewellery and studio walls is modern and frequently detached from any of these liturgical settings.

Sikh scripture's opening formula, Ik Onkar, sits at the very start of the Guru Granth Sahib and is written as a numeral one followed by a character related to the Om syllable, a visual kinship Sikh commentators are generally careful to qualify: the Gurus drew on the wider North Indian devotional vocabulary that included Om while insisting on a strictly monotheistic reading that rejects the pluralist and impersonal readings some later Hindu philosophy gives the same syllable. Jainism's fivefold reading of Om as a contraction of the Panca-Namaskara, homage to the liberated souls, the perfected, the spiritual leaders, the teachers and all ascetics, gives the syllable a devotional rather than cosmological meaning distinct from both the Vedantic and Sikh readings, evidence that a single sound accumulated genuinely different theological content across the traditions that adopted it rather than carrying one stable meaning outward from a single source.