Aum (also Om or Ohm) ॐ is a mystical or sacred syllable in the Hindu, Jain and Buddhist religions. It is placed at the beginning of most Hindu texts as a sacred exclamation to be uttered at the beginning and end of a reading of the Vedas or previously to any prayer or mantra and also is said in the beginning of any puja (religious ritual). The Mandukya Upanishad is entirely devoted to the explanation of the syllable.
With preceding a or ā, the o of om in Sanskrit grammar in sandhi (Sanskrit: संधि, "joining") does not form vriddhi (au) but guna (o) per Pāṇini 6.1.95.
