The n of nis , nikṣa and ninda is changed to a ṇa optionally, when preceded by an upasarga having in it a cause of change.,
Thus प्रणिंसनम् or प्रनिंसनम्, प्रणिक्षणम् or प्रनिक्षणम्, प्रणिन्दनम् or प्रनिन्दनम् ॥
These verbs are written with ण in the Dhatupatha, and therefore by rule 8.4.14 ante, the change of न into ण would have been obligatory. The present sutra makes it optional. The root णिसि means 'to kiss', णिक्षि रोषणे, and णिदि कुत्सायाम् ॥,