Pāṇini sūtras

The affix chha (īya) comes in the Chhandas, in the fivefold senses taught in V.1.79, 80, after a stem ending with vatsara.

1. vatsara+antātवत्सर+अन्तात्

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   vव्	vatsaraवत्सर	vatsaraवत्सर	vatsara [word]	vatsarवत्सर् + plus aअ
   aअ	antaअन्त	antātअन्तात्	end	antअन्त् + plus ātआत्

2. chaḥछः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   cच्	chaछ	chaḥछः	īyaईय	chछ् + plus aḥअः

3. chandasiछन्दसि

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   cच्	chandasछन्दस्	chandasiछन्दसि	Veda	chandछन्द् + plus asiअसि

Anuvṛtti

1. ṭhañठञ् 5·1·18

   Part	Lexeme	Sandhi form	Meaning	Stem
   ṭट्	ṭhañठञ्	ṭhañठञ्	ṭhañठञ्	ṭhañठञ्

2. kālātकालात् 5·1·78

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   kक्	kālaकाल	kālātकालात्	time	kālकाल् + plus ātआत्