Pāṇini sūtras

When a word denotes ‘cause,’ it takes the third case affix.

1. hetauहेतौ

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   hह्	hetuहेतु	hetauहेतौ	cause	hetहेत् + plus auऔ

Anuvṛtti

1. a+abhinihiteअ+अभिनिहिते 2·3·1

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	naन	aअ	not	naन
   aअ	abhidhāअभिधा	abhinihiteअभिनिहिते	express	abhihitअभिहित् + plus iteइते

2. tṛtīyāतृतीया 2·3·18

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   tत्	tṛtīyतृतीय्	tṛtīyāतृतीया	instrumental	tṛtīyतृतीय् + plus āआ