In every Mantra the prefix of Namah is generally added. Just for example Namah Sivaya. Now this Mantra is practically indicating the holy name of Lord Siva. Na means negation and Ma means false ego or Ahamkara. Therefore Namah means surrendering to the name Siva. In other words to accept the supremacy of Lord Siva means Namah Sivaya. Therefore the conclusion is that in Mantra the name of the deity is unavoidably amalgamated. And in the Mantra the spiritual power, by the Rsis like Narada etc. is surcharged like the copper is electrified by magnetic force. The etymological alphabets are so surcharged with spiritual potency and as such all Mantra indicating the transcendental holy name of God or Godhead is to be understood in that way. When we chant the Mantra as were presented by the authorities—the process helps communication with the personality of Godhead by the sound waves as we have now experienced in the material world of physical waves vibrations. The powerful Mantras have such potency if they are sounded in the right direction. And by chanting the Mantras only one can spiritualise the whole existence as heat can expand on the spherical objects. Mantra Siddhi means complete liberation. Therefore, there is no difference between the holy name and Mantra. Man means mind and tra deliverance. That which delivers one from mental speculation is called “Mantra”. “Mantra Siddhi” is to transcend the gross and subtle mental plane.
In this age all the Mantras that can help us reaching perfection up to the plane of Godhead has been still more concentrated into the Hari-nama. We find therefore in the Brhannaradiya Puranam a particular stress on Harinama which is stated as follows:
harinama harinama harinama eva kevalam
kalau nastyeva nastyeva nastyeva gatir anyatha
Ref >> Srila Prabhupada Vani.