Pāṇini sūtras

The Participial affix does not take the augment iṭ after the root kaṣ, when the participle means ‘difficult’ and ‘impenetrable’.

1. kṛcchra+gahanayoḥकृच्छ्र+गहनयोः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   kक्	kṛcchraकृच्छ्र	kṛcchraकृच्छ्र	difficult	kṛcchrकृच्छ्र् + plus aअ
   gग्	gahanaगहन	gahanayoḥगहनयोः	impenetrable	gahanगहन् + plus ayoḥअयोः

2. kaṣaḥकषः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   kक्	kaṣकष्	kaṣaḥकषः	kaṣकष्	kaṣकष् + plus aḥअः

Anuvṛtti

1. na+iṭन+इट् 7·2·8

   Part	Lexeme	Sandhi form	Meaning	Stem
   nन्	naन	naन	not	naन
   iइ	iṭइट्	iṭइट्	iṭइट्	iṭइट्

2. niṣṭhāyāmनिष्ठायाम् 7·2·14

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   nन्	niṣṭhनिष्ठ्	niṣṭhāyāmनिष्ठायाम्	niṣṭhāनिष्ठा	niṣṭhनिष्ठ् + plus āyआय्