अन्तोदात्तादुत्तरपदादन्यतरस्यामनित्यसमासे

The same case endings may optionally have the acute accent, if the monosyllabic word stands at the end of a compound, and has acute accent on the final, when the compound can be easily unloosened.
The phrases "एकाचः" and तृतीयादिर्विभक्तिः are understood here also. The nitya or invariable compounds are excluded by this rule. Thus प॒र॒म॒वा꣡चा or प॒र॒म॒वाचा꣡, परमवा꣡च or वा॒चे꣡; प॒र॒म॒वाचः꣡ or वा॒चः꣡ ॥ So also परमत्व꣡चा or त्वच꣡ &c. According to 6.1.223, the compounds have acute accent on the final: that rule applies in the alternative when the case-affixes are not acute and gives us
the alternative forms. Why do we say 'is acutely accented on the final'? Observe अ꣡वाचा, सु꣡वाचा, सु꣡त्वचा ॥ These are Tatpurusha compounds and by 6.2.2. the first term of the compound retains its original accent. Why have we used the word 'standing at the end of a compound' when the word नित्यसमासे indicated that the compound was meant ? Had we not used the word उत्तरपदात्, the aphorism would have stood as, अन्तोदात्तादन्यतरस्यामनित्यसमासे 'In a loose-compound having acute on the final, the above affixes are acute, if the compound consists of a monosyllable'. The word एकाचः will thus qualify the compound and not the second member of the compound, which is intended. And thus the rule will apply to श्वोर्क् (शुन ऊर्क्) Instrumental श्वोर्जा, श्वोर्जेः &c, and not to compounds having more than one syllable. Why do we say 'in loose compounds'? Observe अग्नि॒चि꣡ता, सो॒मसु꣡ता ॥ These words form invariable (nitya) compounds by 2.2.19, and by 6.2.139, the second member retains its original accent, which makes चि udatta.