Mantras are often called combination of mystic syllables. They are called mystic because, understanding the intricacies of syllables is beyond normal human comprehension. There are two aspects of mantras. The first one is individual syllables or combinations of syllables. The second one is word. Vedas contain multiple syllables leading to innumerable words that form verses. A word is a combination of more than one syllable. Let us take Śiva (शिव) as an example, which consists of śi and va (शि and व). Again शि is not a single syllable. It contains two alphabets or akṣara-s śa and i (शand इ), where va (व) is a single alphabet or akṣara. A word conveys a meaning. When we say Śiva, at least we know to whom we are referring to. But an akṣara or a bīja does not convey any specific thing. They work on the subtle bodies and not on the gross bodies.
Bīja is a combination of more than one akṣara. Bīja-s are used in mantras pertaining to various deities. For example, raṁ (रं) is known as Agni bīja and signifies god Agni. Bīja raṁ (रं) is made up of akṣara ra (र) and a dot on the top of the akṣara, which is known as bindu. Bindu is the most powerful aspect of a bīja and signifies oneness with Śiva and this is the reason for the highest level of its potency. It infuses the essence of energy into the akṣara or akṣara-s. Without this bindu, the potency of an akṣara would be lost. This bindu is known as anusvāra, which produces the nasal sound of any akṣara or akṣara-s. This bindu alone does not work. Bindu becomes effective, only if it is combined with ma (म). For example kaṁ (कं) consists of ka + ṁ. There cannot be a bindu without ma (म), which is known as labial nasal and is the cause for union of upper lip and lower lip to produce vibrations in the body. Recitation of ṁ activates kuṇḍalinī energy and makes it move towards higher chakras, particularly ājñācakra and sahasrāra. Ma (म) is also known as candrabindu (moon like spot causing nasal sound) and controls the five primary elements, known as pañcabhūta-s – ākāśa, air, fire, water and earth. As far as ma (म) is concerned, it balances pañcabhūta-s in the equal proportion in bīja-s. Every bīja has predominance of any one of the pañcabhūta-s and by using ma (म) at the end of a bīja, pañcabhūta-s are effectively balanced, so that none of the pañcabhūta-s affect the aspirant. It is the primary duty and responsibility of a Guru to analyze the nature of his disciple and initiate appropriate mantras so that the disciple can comfortably move up in spiritual path.
Ma (म) is also known as Nāda, which refers to Parāśaktī. By ending all the bīja-s with मँ (maṁ), bīja-s are energized. For example, let us take Kālī bīja krīṁ (क्रीं), where ka (क) refers to Kālī; ra (र) refers to Brahmā; ī (ई) refers to Mahāmāyā (this is the state between suddhavidyā and māyā tattva-s);Nāda (ma - म) refers to Parāśakti and the bindu on the top of ma – म refers to Śiva. Therefore, the one who recites krīṁ (क्रीं) is energized with the energies of Kālī, Brahmā, Mahāmāyā, Parāśakti andŚiva. Regular recitation of this bīja krīṁ (क्रीं) cause necessary modifications in the energy level of the one, who recites regularly and this practice is known as sādhana , which forms the most important part of Śakti worship. In order to have complete effect of bīja-s in the energy level of the body, each bīja is arranged in a particular order and a number of such bīja-s form one mantra. Therefore, a mantra becomes effective only if all the bīja-s are properly understood and recited.
But this is not just a dot. This dot comprises of ardacandra, rodhinī, nāda, nādānta, śakti, vyāpikā, samanā and uṇmanī. Beginning from bindu and including these eight, is Nāda (total nine). This Nāda comprises of two V-s one above the other (each V has two lines and two V-s together have four lines) and four dots each at the open ends of V and one Bindu or the dot at the top of a bīja though appears very tiny, is the most powerful aspect of a dot on the top these four dots. More than these V-s and dots, the pronunciation is important. There are specifications of length of timing for pronunciations of each bīja. There are guidelines for pronouncing the bīja-s. Unless these guidelines are understood and practiced as per the guidelines, none of the mantras will fructify. Further, mantras should not be recited without out sound in the initial stages. The first practice is to recite them aloud so that the every bīja of a mantra energises the body and bring in alignment all the five principle elements of the body in a proper manner. Secondly, recitation of mantra with sound alone causes the kuṇḍalinī to ascend to the upper chakras due to vibrations caused by the the union of Nāda (Śakti) and Bindu (Śiva).
On the other hand, recitation of name of a god or goddess in the form of a word will have significant impact on the mind. For example, recitation of Namaśivāya or Parāśaktī brings forth a form of Śiva or Śakti in the mind of the aspirant. When more number of repetitions are made, thought about Śiva or Śakti strongly pervades the mind, as during every recitation, their forms get embedded strongly in his mind, driving away mundane thought processes. Though these are also called mantras, technically speaking, they are words that cause powerful changes in thought processes of the practitioner. Great sages like Śaṁkarācārya concentrated on poetic compositions rather than formulating mantras. They however concentrated only on praṇava (OM) mantra, which encompasses all other mantras. Though mantras are widely practiced now, they fail to confer any benefits on the practitioner because of the reasons discussed above.
The mahāvākya-s such as “ahaṁ brahmāsmi” or “I am That” do not have any mystical syllables, not even praṇava (ॐ). They are strong affirmative words that work wonders in the mind and repeated affirmations make things happen much faster.