Nyasa

Etymology

Nyasa means purifying.

Introduction

Anga Nyasa & Kara Nyasa In Puja

Nyasa means purifying. That's why Anga Nyasa, and Kara Nyasa. You invoke the sacred sound to purify the Anga (body parts) and Kara (hands).

Sannyas

Sanyas means purifying everything! Sarva Nyasa is Sanyasa. Here you invoke the Divine itself to purify everything!

References

http://www.nithyananda.org/video/responsibility-makes-shava-shiva#gsc.tab=0