Pāṇini sūtras

And also after the word that stands last in the above list (i. e. puṇya) and eka, this substitution does not take place.

1. uttama+ekābhyāmउत्तम+एकाभ्याम्

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   uउ	uttamaउत्तम	uttamaउत्तम	last	uttamउत्तम् + plus aअ
   eए	ekaएक	ekābhyāmएकाभ्याम्	eka [word]	ekaएक + plus bhyāmभ्याम्

2. caच

   Part	Lexeme	Sandhi form	Meaning	Stem
   cच्	caच	caच	besides	caच

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

4. naन 5·4·89

   Part	Lexeme	Sandhi form	Meaning	Stem
   nन्	naन	naन	not	naन