After the verbs 1. yaj 'to worship' 2. yāc 'to ask for' 3. yat 'to strive' 4. vicch 'to shine' 5. pracch 'to ask' 6. rakṣ 'to preserve', comes the affix naṅ with the force of denoting mere action etc.,
The conditions of sutras 18 and 19 are understood here also. The ङ् of नङ् is for the sake of prohibiting guna or vriddhi (I. I. 5); as यज्ञः 'sacrifice'; याच्ञा 'solicitation'; यत्नः 'effort'; विश्नः 6.4.19 'lustre'; प्रश्नः 'a question'; रक्ष्णः 'protection.
The root प्रच्छ, by 6.1.16, ought to have changed its र into ॠ before the ङित् affix नङ्. Its not doing so must be taken to be an irregularity countenanced by Panini, as we know from the fact that Panini himself uses the form प्रश्नः in (III. 2. II7).,