The sacred syllable AUM (OM) stands for the Absolute. OM is the Akshra or Imperishable i.e. GOD. It is the most powerful Hindu Mantra. It is composed of five elements; the syllables A,U,M the dot or BINDU and the sound (nada). It is revered as the representative of the Gods. It is considered as the very essence of the Vedas. All aspects of speech are believed to have come forth from this word.
OM first appears in the Upanishads as a mystic monosyllable and is regarded as the seed or basis of all Mantras. The past, the present and the future are all included in this one sound. In the Upanishads AUM is described as PRANAVA (Nu means praise and Pra means Superior. Hence OM means Superior or Best praise or prayer.
OM is said to be the first sound to have come from The Creator’s mouth and is thus said to be foundation of all sounds. 'A' is the root sound produced without touching any part of the tongue or palate. 'M' represents the last sound in the series being pronounced by closed lips. All other sounds exist between these two. In the Christian Bible, AUM is mentioned as the Word.' In the beginning was the Word, and the Word was with God, and the Word was God 'The exact parallel in Rig Veda reads '. In the beginning was Brahman, with whom was the Word (OM or AUM) and the Word was truly the Supreme Brahman'. The word AUM, Christian’s Amen, and the Mohammedan’s AMIN, all represent one and the same.
The three syllables of AUM also represent the TRIMURTI; 'A' represents Vishnu, 'U' represents Shiva and 'M' represents Brahma and thus represents Creation. Preservation and Destruction.
Because of this mystic importance 'OM' is uttered at the beginning of all prayers and religious ceremonies and also at the beginning of all Mantras.
'OM' is the best known and most used symbol of Hinduism.