That scripture explains that OM is composed of four parts, namely A, U, M, and anusvara (the nasal after-sound or vibration at the end of the M sound, which represents a nasal humming). In Sanskrit, this after-sound is represented by a dot placed above the letter “m.” These four parts symbolically correspond to the Four States of Consciousness:

A—The state of wakefulness, where we experience things externally through our mind and sense organs.

U—The dream state, in which inward experiences are available.

M—The state of deep sleep.

Turya (the “fourth”)—Represented by the nasal humming at the end of the M sound, it is the transcendental Self beyond the mind.

It is the most sacred syllable symbol and mantra of Brahman, the highest Universal Principle, the Ultimate Reality.