The Maitrayaniya Upanishad in sixth Prapathakas (lesson) discusses the meaning and significance of Om. The text asserts that Om represents Brahman-Atman. The three roots of the syllable, states the Maitri Upanishad, are A + U + M. The sound is the body of Soul, and it repeatedly manifests in three: as gender-endowed body - feminine, masculine, neuter; as light-endowed body - Agni, Vayu and Aditya; as deity-endowed body - Brahma, Rudra and Vishnu; as mouth-endowed body - Garhapatya, Dakshinagni and Ahavaniya; as knowledge-endowed body - Rig, Saman and Yajur; as world-endowed body - Bhūr, Bhuvaḥ and Svaḥ; as time-endowed body - Past, Present and Future; as heat-endowed body - Breath, Fire and Sun; as growth-endowed body - Food, Water and Moon; as thought-endowed body - intellect, mind and psyche. Brahman exists in two forms - the material form, and the immaterial formless. The material form is changing, unreal. The immaterial formless isn't changing, real. The immortal formless is truth, the truth is the Brahman, the Brahman is the light, the light is the Sun which is the syllable Om as the Self.