The augment nuk (n) is added after the short a of a reduplicate in the Intensive (with expressed or elided yaṅ) when the root ends in a nasal.,
As तन्तन्यते and तन्तनीति; जङ्गम्यते and जङ्गमीति, यंयम्यते and यंयमीति; रंरम्यते and रंरमीति ॥ The augment न् here should be considered as anusvara, because an adesa is indicated by the nature of the sthanin which is replaced; and therefore in यंयम्यते, it remains anusvara. Had it been म्, it could not have been changed to anusvara in यंयम्यते, रंरम्यते (See 8.3.24). In तन्तन्यते &c, the anusvara is changed to न्, ङ् &c, by 8.4.58; the other forms तन्तन्यते तंतनीति, जंगम्यते, जंगमीति are derived by the following :-
Vart:- This anusvara should be treated as if it was at the end of a Pada or word. That being so, 8.4.59 applies, and we have the anusvara unchanged, as in तंतन्यते &c.
Why do we say \after a short अ\? Observe तेतिम्यते ॥ The त् in अत् indicates that the augment will not be added to a reduplicate which once was long आ but became short by 7.4.59 as from भाम 'to be angry', is बाभाम्यते, (the second lengthening takes place by 7.4.83). Why do we say ending in a nasal? Observe पापच्यते ॥,