In the Indian religions, a mantra (Devanāgarī मन्त्र) is a sound, syllable, word, or group of words that are considered capable of "creating transformation" (cf. spiritual transformation). Their use and type varies according to the school and philosophy associated with the mantra. Other purposes have included religious ceremonies to accumulate wealth, avoid danger, or eliminate enemies. Mantras originated in the Vedic tradition of India, later becoming an essential part of the Hindu tradition and a customary practice within Buddhism, Sikhism and Jainism. The use of mantras is now widespread throughout various spiritual movements which are based on, or off-shoots of, the practices in the earlier Eastern traditions and religions.
Mantras can be interpreted to be effective as vibration, or more simply as sound, which may include verbal repetition, in the form of chanting, or internal mental repetition. For this reason great emphasis is put on correct pronunciation (resulting in an early development of a science of phonetics in India). Mantras can be used in Eastern spiritual traditions to divert the mind from basic instinctual desires or material inclinations, by focusing the mind on a spiritual idea, such as "I am a manifestation of divine consciousness".
In English language usage, the term "mantra" has a colloquial meaning quite distinct from prayer, and carries the interpretive (or misinteretive) and derogatory connotations based in monotheism's negative view of polytheism and many of its concepts. In short, "mantra" in English carries a negative connotation of 'mindless or thoughtless repetition of a concept,' similar to the negative connotations associated with the term "dogma."
In the context of the Vedas, the term mantra refers to the entire portion which contains the texts called Rigveda, Yajur or Saam, that is, the metrical]] part as opposed to the prose Brahmana commentary. With the transition from ritualistic Vedic traditions to mystical and egalitarian Hindu schools of Yoga, Vedanta, Tantra and Bhakti, the orthodox attitude of the elite nature of mantra knowledge gave way to spiritual interpretations of mantras as a translation of the human will or desire into a form of action, with some features in common with spells in general.
For the authors of the Hindu scriptures of the Upanishads, the syllable Aum, itself constituting a mantra, represents Brahman, the godhead, as well as the whole of creation. Kūkai suggests that all sounds are the voice of the Dharmakaya Buddha ; i.e. as in Hindu Upanishadic and Yogic thought, these sounds are manifestations of ultimate reality, in the sense of sound symbolism postulating that the vocal sounds of the mantra have inherent meaning independent of the understanding of the person uttering them. Nevertheless, such understanding of what a mantra may symbolise or how it may function differs throughout the various traditions and also depends on the context in which it is written or sounded. In some instances there are multiple layers of symbolism associated with each sound, many of which are specific to particular schools of thought. For an example of such see the syllable: Aum which is central to both Hindu and Buddhist traditions.
While Hindu tantra eventually came to see the letters as well as the sounds as representatives of the divine, it was when Buddhism travelled to China that a major shift in emphasis towards writing came about. China lacked a unifying, ecclesiastic language like Sanskrit, and achieved its cultural unity by having a written language that was flexible in pronunciation but more precise in terms of the concepts that each character represented. The Chinese prized written language much more highly than did the Indian Buddhist missionaries, and the writing of mantras became a spiritual practice in its own right. So that whereas Brahmins had been very strict on correct pronunciation, the Chinese, and indeed other Far-Eastern Buddhists were less concerned with this than correctly writing something down. The practice of writing mantras, and copying texts as a spiritual practice, became very refined in Japan, and the writing in the Siddham script in which the Sanskrit of many Buddhist Sutras were written is only really seen in Japan nowadays. However, written mantra-repetition in Hindu practices, with Sanskrit in any number of scripts, is well-known to many sects in India as well.
Mantras, the Sanskrit syllables inscribed on yantras, are essentially 'thought forms' representing divinities or cosmic powers, which exert their influence by means of sound-vibrations. Khanna, Madhu (2003). Yantra: The Tantric Symbol of Cosmic Unity. Inner Traditions. ISBN 0892811323 & ISBN 978-0892811328. p.21
The Sanskrit word mantra- (m. मन्त्रः, also n. मन्त्रं) consists of the root man- "to think" (also in manas "mind") and the suffix -tra meaning, tool, hence a literal translation would be "instrument of thought".
Another explanation is that the suffix -tra means "protection".
The Chinese translation is zhenyan 眞言, 真言, literally "true words", the Japanese on'yomi reading of the Chinese being shingon (which is also used as the proper name for the prominent esoteric Shingon sect).