Pāṇini sūtras

The affix yak comes after a root, when a sārvadhātuka (III.4.113) follows, denoting the action or the object.

1. sārvadhātukeसार्वधातुके

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	sārvadhātuसार्वधातु	sārvadhātukeसार्वधातुके	sārvadhātukaसार्वधातुक	sārvadhātukसार्वधातुक् + plus eए

2. yakयक्

   Part	Lexeme	Sandhi form	Meaning	Stem
   yय्	yakयक्	yakयक्	yakयक्	yakयक्

Anuvṛtti

1. dhātoḥधातोः 3·1·22

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

2. bhāva+karmaṇoḥभाव+कर्मणोः 3·1·66

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   bब्	bhāvaभाव	bhāvaभाव	action	bhāvभाव् + plus aअ
   kक्	karmanकर्मन्	karmaṇoḥकर्मणोः	object	karmकर्म् + plus aṇo&अणो&