In a compound, the second member of which contains a guttural, there is ṇa in the room of na , that follows anything which standing in the prior member is qualified to cause the change, provided the na be at the end of a prātipadika , or be the augment num , or occur in a vibhakti,
If the second part of a compound contains a letter of the class क्, the change is obligatory, even though the second part be not monosyllabic. As वस्त्रयुगिणौ, वस्त्रयुगिणः, स्वर्गकामिणौ, वृषगामिणौ ॥ नुम् :- वस्त्रयुगाणि, खरयुगाणि ॥ विभक्ति :- वस्त्रयुगेण, खरयुगेण ॥
The word वस्त्रयुगिणौ is a compound of वस्त्र with युगिन् (the affix इनिis added first to युग and then the word so formed is compounded with vastra). Thus the न् becomes प्रातिपदिकान्त i.e. it becomes the final of a Nominal-stem, which stands as a second member in a compound.,