Oṃ

(Sanskrit). An ancient Indian sacred syllable. Various complex explanations of its meaning are found in exegetical literature and it characteristically prefixes most mantras used in Buddhism. It becomes a symbol of spiritual knowledge, especially of emptiness (śūnyatā), in Mahāyāna and tantric Buddhism.

The Vedic (see Vedic entries) Upaniśads (see Upaniṣads) tell us that the syllable oṃ (auṃ) is the “primary sound … the one indestructable thing or syllable (akśra).” Recited as a mantra (see Mantra), for example, at the beginning and end of prayers—something approximating the Christian amen but much more important—it is a sound that expresses the divine. The Katha Upanisad says that meditation on oṃ can bring one to union with the Absolute—that is, with Brahman (see Brahman). In a sense, Oṃ is Brahman and the cosmos itself. In keeping with this idea, the Māṇḍūkya Upaniśd breaks the syllable into its connected components, a, u, and m. It relates a to being awake, u to dreaming, m to a sleep without dream, and the whole auṃ, or oṃ, to the turīya state—that which is Brahman. The same Upaniśd speaks of the use of the oṃ in meditation, the sacred syllable being the bow; the Ātman (see Ātman), or Self, being the arrow; and Brahman being the target. Eventually the oṃ, as the sound of the contraction of a, u, and m was related to the trimūrti of Brahmā (see Brahmā), a as creating; Viṣṇu (see Viṣṇu), u as sustaining; and Śiva (see Śiva), m as dissolving.