Pāṇini sūtras

This substitution of ahna for ahan, does not take place after a Numeral, when it forms a Collective noun meaning a number of days taken as a unity.

1. naन

   Part	Lexeme	Sandhi form	Meaning	Stem
   nन्	naन	naन	not	naन

2. saṅkhyā+ādeḥसङ्ख्या+आदेः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	saṃkhyāसंख्या	saṅkhyāसङ्ख्या	numeral	saṃkhyसंख्य् + plus āआ
   āआ	ādiआदि	ādeḥआदेः	beginning	ādआद् + plus eḥएः

3. samāhāreसमाहारे

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	samāhāraसमाहार	samāhāreसमाहारे	group	samāhārसमाहार् + plus eए

Anuvṛtti

1. samāsa+antāḥसमास+अन्ताः 5·4·68

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	samāsaसमास	samāsaसमास	Sanskrit compound	samāsसमास् + plus aअ
   aअ	antaअन्त	antāḥअन्ताः	end	antअन्त् + plus āMआM

2. tatpuruṣasyaतत्पुरुषस्य 5·4·86

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   tत्	tatpuruṣaतत्पुरुष	tatpuruṣasyaतत्पुरुषस्य	tatpuruṣaतत्पुरुष	tatpuruṣतत्पुरुष् + plus asyaअस्य

3. ahnaḥअह्नः 5·4·88

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	ahnaअह्न	ahnaḥअह्नः	ahna [word]	ahnअह्न् + plus aḥअः