Pāṇini sūtras

d or ru may optionally be substituted for the s of a root, before the Personal ending si (s), when such s stands at the end of a Pada.

1. sipiसिपि

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	sipसिप्	sipiसिपि	sipसिप्	sipसिप् + plus iइ

2. dhātoḥधातोः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   dद्	dhātuधातु	dhātoḥधातोः	Sanskrit verbal root	dhātधात् + plus oḥओः

3. ruḥ+vāरुः+वा

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   rर्	ruरु	ruḥरुः	ruरु	rर् + plus uḥउः
   vव्	vāवा	vāवा	optionally	vāवा

Anuvṛtti

1. daḥदः 8·2·72

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   dद्	daद	daḥदः	dakāraदकार	dद् + plus aḥअः