Om Namasivaya :

Mantra is the sound-body of a god; Yantra depicts the sound-body in a diagram. Mantra = (Man = to think or meditate + Tra = to protect or liberate.) The word 'man' comes from Sanskrit meaning 'to think.' Manitan (மனிதன்) in Tamil also means Man. Thus, man is a thinking animal. That which thinks is Manas (= mind). Yantra = instrument, engine, apparatus, amulet with mystical diagram endowed with protective occult powers. Sanskrit letters are strung together like a wheel called Matrikachakra. 

 

You know A is the first letter and Z is the last letter. All Sanskrit letters are sacred. The first letter is 'a' (अ) and the last letter is h (ह) ; 'a' is dynamic Siva starting creation and 'h' is resting Siva in that creation has come to a standstill. The first letter and the last letter encompass all the letters between them. Letters 'a' and 'ha' (अ and ह) are combined with a terminal 'm' resulting in 'Aham', which is the Mantra of Siva. 

 

All the vowels abide in Siva; all the consonants from ka to ṣa (क + ष) abide in Sakti and thus Her Mantra is Kṣa-क्ष (= क् + ष) . Mantra Hamsa: Ha (ह the vowel) is Siva and ṣa (ष the consonant) is Sakti.