If you've attended a yoga class before, you've probably been led through a round or two of "Om" chanting at the beginning or end. Unless you practice Hinduism, that might be your only experience with Om, but it's actually a sacred symbol and syllable. And yes — its significance extends far beyond any boutique yoga class.
Om, sometimes spelled Aum, appears in several of the Upanishads (the founding philosophical texts in Hinduism) and is described as the most important mantra for worship. It's meant to be spoken at the beginning and end of prayers, meditations, and chants in order to clear away spiritual obstacles and to reaffirm the intentions of the rite once it's over. It's even used in similar rituals within Jainism and Buddhism.
Given its widespread use in Hinduism and other religions, Om's meaning is fittingly far-reaching. Usually pronounced as "a-u-m," Om's sound and symbol are believed to illustrate unity between the "three worlds" in Hinduism: earth, heaven, and atmosphere. But that isn't the only trio Om is said to embody. It may also represent the three major Hindu gods (Brahma, Vishnu, and Shiva) or the three sacred Vedic scriptures (Rigveda, Yajurveda, and Samaveda).
Even the design for Om's symbol is sacred, with each curve, dot, and stroke symbolizing a key component of the mind. The bottom-most curve on the left reflects the waking mind, the curves above that illustrate the mind in deep sleep, the curve to the far right reflects the dreaming mind, and the dot represents the fourth, unknown state of consciousness, which is believed to be so far from the human experience that it must be separated by the semicircle you see beneath the dot. Altogether, Om is the sum of all four states of consciousness.
Now that you're a little more familiar with Om's spiritual significance, let's go back to that yoga class. Since yoga is a major part of Indian philosophy and often involves meditation, chanting "Om" at the opening and closing of a practice is totally appropriate. It serves as a reminder that yoga is, at its core, an exercise in spiritual development. Plus, chanting Om has even been found to promote a quieter mental state — which is exactly what we're looking for when we hit the mat.