7.2.116
अत उपधायाः
Operational rule vidhi
The उपधा-अकार of an अङ्ग undergoes a वृद्धिः when followed by a णित् or a ञित् प्रत्यय.
Word by word (padaccheda)
Target अतः ṣaṣṭhī · ekavacanaTarget उपधायाः ṣaṣṭhī · ekavacana
- Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
Dotted words are technical terms, dashed ones pratyāhāras (names for classes of sounds or affixes). Hover or tap one to see its card.
Full reading
अतः उपधायाः
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
Commentary
In a अङ्ग (stem) ending in a consonant with an अ immediately preceding it, the वृद्धि is substituted for such अ when followed by an indicatory ञ् or ण्।
As पाकः, त्यागः, यागः with घञ्, पाचि with the causative णि, पाचकः with ण्वुल् ॥ Why do we say 'अ'? Observe भेदयति, भेदकः with guna only from भिद् where इ is penultimate and not अ ॥ Why do we say 'penultimate'? Observe चकासयति, तक्षकः ॥
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.