Mantra (Sanskrit) That portion of the Vedas which consist of hymns as distinct from the Brahmana and Upanishad portions. The mantras considered esoterically were originally as magical as they were religious in character, although the former today is virtually forgotten, although remembered as a fact which once was. In the composing of the mantras the rishis of old knew that every letter had its occult significance, and that the vowels especially contain occult and even formidable potencies when properly chanted. The words of the mantra were made to convey a certain hid meaning by certain secret rules involving first the secret potency of their sound, and incidentally the numerical value of the letters; the latter however was relatively unimportant. Hence their merely verbal significance is something quite different from their meaning as understood of old. 
The language of incantations or mantras is the element-language composed of sounds, numbers, and figures. He who knows how to blend the three will call forth the response from the regent-god of the specific element needed. For, in order to communicate with the gods, men must learn to address each one of them in the language of his element. Sound is "the most potent and effectual magic agent, and the first of the keys which opens the door of communication between Mortals and the Immortals" (SD 1:464). The hidden voice or active manifestation of the latent occult potency of the mantras is called vach. The would-be magician attempting to evoke the "spirits of the vasty deep" by uninstructed chanting or singing of any ancient mantras will never succeed in using the mantras effectively in a magical way, until he himself has become so cleansed of all human impurities as to be able at will and with inner vision to enter into communion if not direct confabulation with the inner realms. 
The Scandinavian runes in certain respects correspond to the Hindu mantras.