When it is prefixed with a pranav it becomes Om namaha Shivaya, the six lettered ( shadakshari) mantra. In a subdivision of the Yajurveda the Rudradhyay begins with these words.
The five lettered ( panchakshari) mantra: ' Namaha Shivaya (नम: शिवाय ।)' is the five lettered mantra of Shiva.
