The affix ṅīp comes in the feminine after a bahuvrīhi samāsa beginning with a Numeral and ending with the words 1. dāman 'a rope' and 2. hāyana 'a year'.,
The word दामन् was liable to be operated upon by three rules, by, 4.1.13 ordaining डाप्, by 4.1.11 prohibiting totally the affixing of ङीप् and 4.1.28 ordaining nip optionally : the present sutra ordains nip to the exclusion of all those rules. As द्विदाम्नी 'a (mare) bound by two ropes'. त्रिदाम्नी ॥
Similarly हायन would have taken long आ by 4.1.4, this ordains long ई ॥ Thus द्विहायनी 'two years (old girl)', त्रिहायणी; चतुर्हायणी ॥
Vart:- The word 'hayana' must denote 'age', for the purposes of this sutra. Therefore we have no nip here:- द्विहायना शाला 'a hall of two years existence'. So also त्रिहायना and चतुर्हायना ॥ Moreover in these latter cases the न is not changed into ण; for when हायन denotes 'age', it is then only that the न is changed into ण and not otherwise.,