Om Nama Shivaya and Shivaya Nama are mantras dedicated to Mahadev Shiva. But is there a difference between them?
Shivaya Nama – Sookshma Panchakshara
Om Nama Shivaya is chanted to gain worldly objectives.
Shivaya Nama is chanted to attain Moksha – Liberation
Saint Vallalar wrote that when one applied sacred ash on the forehead, one should say ‘Sivaya Namaha,’ because it confers on a devotee good speech, good company, good qualities and moksha.
K. Sambandan explains about the difference in an article in The Hindu.
Each of the letters in these mantras has significance. ‘Na’ represents our pride, ‘Ma’ represents the impurities in our minds, ‘Si’ represents Lord Siva, ‘Va’ represents Goddess Sakti, and ‘Ya’ represents the atma. So when we say, ‘Sivaya Namaha,’ the atma, represented by ‘ya,’ is in the middle. On one side are pride and other impure thoughts represented respectively by ‘Na,’ and ‘Ma.’ On the other side of ‘ya,’ we have Lord Siva and Goddess Sakti represented by ‘Si’ and ‘
Va.’ So it is for us to decide what we are going to do. Will we go the way in which temptation leads us? Or will we turn towards God? The ‘ya’ comes right next to ‘Va,’ for the Goddess is even more merciful than Lord Siva. After all, an erring child is afraid to approach its father. It first seeks forgiveness from its mother, who recommends to the father that he must not judge his child harshly. In the same way, the Goddess makes sure that the Lord’s wrath is not directed towards us. She speaks to Him on our behalf. To get His mercy, we must go to Her first. His mercy then automatically comes to us.