Pāṇini sūtras

The word nirvāṇa is irregularly formed by changing the Nishṭhâ ta to na, when the sense is not that of ‘wind’.

1. nirvāṇaḥनिर्वाणः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   nन्	nirvāṇaनिर्वाण	nirvāṇaḥनिर्वाणः	nirvāṇa [word]निर्वाण [wओर्द्]	nirvāṇनिर्वाण् + plus aḥअः

2. a+vāteअ+वाते

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	aअ	aअ	not	aअ
   vव्	vātaवात	vāteवाते	wind	vātवात् + plus eए

Anuvṛtti

1. niṣṭhā+taḥनिष्ठा+तः 8·2·42

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   nन्	niṣṭhनिष्ठ्	niṣṭhāनिष्ठा	niṣṭhāनिष्ठा	niṣṭhनिष्ठ् + plus āआ
   tत्	tत्	taḥतः	takāraतकार	tत् + plus aḥअः