Pāṇini sūtras

And the affix ‘ap’ comes optionally after the verb ‘yam’, when the upasargas ‘sam’, ‘upa’ ‘ni’ and ‘vi’ are in composition; or even when it is upasarga-less.

1. yamaḥयमः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   yय्	yamयम्	yamaḥयमः	yamयम्	yamयम् + plus aḥअः

2. sam+upa+ni+viṣuसम्+उप+नि+विषु

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	samसम्	samसम्	samसम्	samसम्
   uउ	upaउप	upaउप	upaउप	upउप् + plus aअ
   nन्	niनि	niनि	niनि	nन् + plus iइ
   vव्	viवि	viṣuविषु	viवि	vव् + plus iṣuइषु

3. caच

   Part	Lexeme	Sandhi form	Meaning	Stem
   cच्	caच	caच	besides	caच

Anuvṛtti

1. bhāveभावे 3·3·18

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   bब्	bhāvaभाव	bhāveभावे	action	bhāvभाव् + plus eए

2. sañjñāyāmसञ्ज्ञायाम् 3·3·19

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	saṃjñसंज्ञ्	sañjñāyāmसञ्ज्ञायाम्	name	saṃjñसंज्ञ् + plus āyआय्

3. apअप् 3·3·57

   Part	Lexeme	Sandhi form	Meaning	Stem
   aअ	apअप्	apअप्	apअप्	apअप्

4. an+upasargeअन्+उपसर्गे 3·3·61

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	naन	anअन्	not	naन
   uउ	upasargaउपसर्ग	upasargeउपसर्गे	preposition	upasargउपसर्ग् + plus eए

5. vāवा 3·3·62

   Part	Lexeme	Sandhi form	Meaning	Stem
   vव्	vāवा	vāवा	optionally	vāवा