What is the meaning of Om?

Om — sometimes written Aum — is considered the primordial sound in the Vedic tradition. It is described in the Mandukya Upanishad as containing three parts: A, U, and M, corresponding to the waking, dreaming, and deep-sleep states of consciousness, with the silence that follows representing pure awareness beyond all three. Om appears at the start of countless mantras. Chanting Om on its own — held long, letting the sound resonate in the chest and skull — is a full practice. Buddhist traditions also use Om, though understood slightly differently. In both contexts, Om is a sound of arrival, of presence, of return to the ground of being.