Om Namah Shivaya

Oṁ namaḥ śivāya (Sanskrit: ॐ नमः शिवाय; IAST: Om Namaḥ Śivāya) is one of the most popular Hindu mantras and the most important mantra in Shaivism.

Its translation is "salutations (namas) to Shiva", preceded by the mystical syllable "Aum". The syllable "ya" at the end of the mantra denotes an offering. Thus the mantra Om Namah Sivaya actually means "I offer to Siva a respectful invocation of His Name", and not merely "I respectfully invoke His Name". Om Namah Shivaya mantra is sung by devotees in prayers and recited by yogis in meditation. It is associated with qualities of prayer, divine-love, grace, truth, and blissfulness.

Traditionally, it is accepted to be a powerful healing mantra beneficial for all physical and mental ailments. Soulful recitation of this mantra brings peace to the heart and joy to the [Ātman] or Soul. Sages consider that the recitation of these syllables is sound therapy for the body and nectar for the soul [Ātman]. The nature of the mantra is the calling upon the higher self; it is the calling upon Shiva, the destroyer deity, to aid in the death (destruction of ego) and rebirth achieved during meditation. This goes generally for mantras and chants to different gods, which are different aspects of the higher self.

It is called Siva Panchakshara, or Siva Panchakshari, the "five-syllable" mantra (viz., excluding the Om) dedicated to Siva. The Siva Panchakshari mantra is the most holy salutation to Śiva. The Panchakshara can be recited by Shiva devotees during pooja, Japa, Dhyana, homa and while smearing Vibhuti.

The Tamil Saivaite hymn Tiruvacakam begins with the five letters 'na' 'ma' 'ci' 'vaa' 'ya'. It is part of the Shri Rudram Chamakam, a Hindu prayer taken from the Yajurveda, and thus predates the use of Shiva as a proper name, in the original context being an address to Rudra (later Shiva), where śiva retains its original meaning as an adjective, meaning "auspicious, benign, friendly", a euphemistic epithet of Rudra.

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Wikipedia