After na which is added to the roots of the rudhādigaṇaḥ (7th Conjugation) as a gaṇavikaraṇa - śnam (characteristic), there is the elision of the following na,
Thus अनक्ति and भनक्ति from अञ्ज 'to anoint', and भञ्ज 'to break'. Thus अञ्ज् + श्नम् +तिप् = अनञ्ज् + ति (I. I. 47) = अनज् + ति 6.4.23 = अनक्ति ॥ So also हिनस्ति from हिसि (हिन्स्) 'to injure'. Why do we say 'after श्न' and not merely 'after न', without the indicatory श ? Observe यज्ञानाम्, यत्नानाम्, where the न of नाम् is not elided after the न of यज्ञ and यत्न, the lengthening of अ by 7.3.102 being sthanivat would not have prevented the elision. In the case of विश्नानाम् and प्रश्नानाम् (formed by विश्न + नाम् and प्रश्न + नाम्) also, the न of नाम् is not elided after श्न of विश्न ॥ For the श्न of the sutra is the technical श्न the vikarana, and not any combination of the letters श and न ॥ The pratipadokta maxim applies here. लक्षणप्रतिपदोक्तयोः प्रतिपदोक्तस्यैव ग्रहणम् ॥,