अनुनासिकात् परो ऽनुस्वारः

The substitution of nasal is optional by 8.3.2. When nasal is not substituted, we add an anusvara to such vowel. The word अन्य should be read into the sutra to complete the sense, i.e. अनुनासिकात् अन्यो यो वर्णः \a letter other than a nasal\, i. e. a letter for which nasal has not been ordained, and which stands before रु ॥

Thus 8.3.5, teaches substitution of the म् of सम् an anusvara would be added. As संस्कर्त्ता, संस्कर्त्तव्यम् ॥ Similarly 8.3.6, teaches रु substitution of the म् of पुम् ॥ An anusvara will be added here also, as, पुंस्कामा ॥ Similarly 8.3.7, teaches रु substitution of final म् ॥ Here also an anusvara will be added, as भवांश्चरति ॥

Some say \the word परः in the sutra means अन्यः, and so we need not supply the word अन्यः from outside\. They say अनुनासिकात् परः = अनुनासिकादन्यः; i. e. the anusvara takes place in that alternative when there is no nasal. That anusvara is an augment and not a substitute. It is an augment to the vowel which precedes रु ॥,