The affix yat comes in the sense of 'who stays there' after the prātipadika (Nominal Stems) dik etc.,
This debars अण् and छ ॥ As दिशि भवं = दिश्यम् 'lying in a particular quarter', वर्ग्यम् ॥
The words मुख and जघन which ordinarily mean 'mouth' and 'hip' respectively, have not this meaning when this affix is to be added. They must refer to non-corporeal or abstract objects. As सेनामुख्यं 'who stays in the van of the army'. सेनाजघन्यन् 'who stays in the rear of the army'. In fact, the words 'mukha' and 'jaghana' here mean the 'van' and the 'rear' of an army. The word उदक् takes this affix, when the word so formed is a Name. As उदक्या = रजस्वला, otherwise we have औदको मत्स्यः ॥
1 दिश् 2 वर्ग, 3 पूग, 4 गण, 5 पक्ष, 6 धाय्य (धाय्या)7 मित्र, 8 मेधा, 9 अन्तर, 10 पथिन् 11 रहस्, 12 अलीक, 13 उखा, 14 साक्षिन्, 15 देश, 16 आदि, 17 अन्त, 18 मुख, 19 जघन, 20 मेघ, 21 यूथ, 22 उदकात्संज्ञायाम्, 23 न्याय, 24 वंश, 25 वेश (विश) 26 काल, 27 आकाश, 28 अनुवंश ॥,