nā is substituted for the ending ā of the Instrumental -3rd case singular, after the ghi aṅga (stems) when they are not feminine.,
As अग्निना, वायुना, पटुना ॥ Why do we not say आङो मा पुंसि 'मा is substituted for आ in the Masculine'? Answer: In order to form the neuter Instrumentals also, as त्रपुणा, जतुना ॥ Objection: These can be formed by the augment नुम् under rule 7.1.73, and not by the ना of this sutra. Answer: But अमुना will not be so formed as अमुना ब्राह्मणकुले ॥ Because सु substituted for दस् of अदस् 8.2.80 is considered as asiddha or non-existent 8.2.1 for the purposes of the application 7.1.73, and as अमु cannot take नुम्, it will take ना by this rule. Why do we say
ot in the Feminine?\ Observe कृत्या, धेन्वा ॥,