Pāṇini sūtras

The affix âch (ā<?>) comes after the word dakshiṇa, in the sense of astâti, but not as a substitute of the ablative case-affix.

1. dakṣiṇātदक्षिणात्

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   dद्	dakṣiṇaदक्षिण	dakṣiṇātदक्षिणात्	dakṣiṇa [word]दक्षिण [wओर्द्]	dakṣiṇदक्षिण् + plus ātआत्

2. ācआच्

   Part	Lexeme	Sandhi form	Meaning	Stem
   āआ	ācआच्	ācआच्	ācआच्	ācआच्

Anuvṛtti

1. astātiḥअस्तातिः 5·3·27

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	astātiअस्ताति	astātiḥअस्तातिः	astātiअस्ताति	astātअस्तात् + plus iḥइः

2. a+pañcamyāḥअ+पञ्चम्याः 5·3·35

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	aअ	aअ	not	aअ
   pप्	pañcamīपञ्चमी	pañcamyāḥपञ्चम्याः	ablative	pañcamपञ्चम् + plus yāया