Mantra is a sacred utterance, numinous sound, or a syllable, word, phonemes, or group of words that have psychological and spiritual power. The spiritual value of mantra comes when it is audible, visible, or present in thought. Mantra means that mental awareness by which one feels one's identity with the highest reality enshrined in a mantra and thus saves oneself from a sense of separateness and difference characteristic of the world. The form of mantra or mystic syllable or syllables. The mind of the aspirant is so intensely identified with the deity of the mantra that it becomes that mantra itself. Every mantra consists of certain syllables. Muttering of the syllables mechanically is of no avail. The aspirant must identify himself with the deity invoked in the mantra. "When an aspirant with one-pointedness of mind, apprehends that reality which is not within the range of utterance, and thus obtains samavesa (absorption in divine consciousness), then that samavesa is known as sakta.

The use, structure, function, importance and types of mantras vary according to the school and philosophy of Hinduism and of Buddhism. Mantras serve a central role in the tantric school of Hinduism. In this school, mantras are considered equivalent to deities, a sacred formula and deeply personal ritual, and considered to be effective only after initiation.
Mantras are typically melodic, mathematically structured meters, resonant with numinous qualities. At its simplest, the word (Aum, Om) serves as a mantra. In more sophisticated forms, they are melodic phrases with spiritual interpretations such as human longing for truth, reality, light, immortality, peace, love, knowledge and action.