ru is substituted for the final n of a word, with the exception of n of praśān before a chav letter (cha ṭha tha ca ṭa ta) which is followed by an am letter (vowel, semi-vowel and nasal).,
The word अम्परे is to be read into this sutra. The word अप्रशान् in the sutra is in the Nominative case, but it has the force of Genitive.
Thus भवाँश्छादयति or भवांश्छादयति; भवाँश्चिनोति or भवांश्चिनोति; भवाँष्टीकते or भवांष्टीकते, (from the root टीकि 'to go'), भवाँस्तरति or भवांस्तरति ॥
Why do we say 'before a छव् letter'? Observe भवान् करोति ॥ Why do we say 'with the exception of the न् of प्रशान्'? Observe प्रशाम् छादयति, प्रशान् चिनोति ॥ Why do we say 'when अम् follows छव्'? See भवान् त्सरुकः ॥ त्सरु is sword, he who is dexterous in it, is called त्सरुकः (कन् 5.2.64).,