दोषो णौ

Operational rule vidhi

The उपधा letter of the verb root दुष् is converted to ऊकार when followed by the णिच् प्रत्यय.

Word by word (padaccheda)

Target दोषः ṣaṣṭhī · ekavacanaRight context णौ saptamī · ekavacana

Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
Right context Saptamī (7th case): "when X follows", the operation applies to what precedes (1.1.66 तस्मिन्निति निर्दिष्टे पूर्वस्य). Also a condition or domain ("in the sense of").

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

दोषः णौ

Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.

Commentary

The ओ of दोष् is replaced by ऊ before the causative णि।
Thus दूषयति, दूषयतः, दूषयन्ति ॥ Similar reasons as in गोह, may be given for the root दुष being exhibited as दोष in the sutra. When not followed by णि, we have दोषो वर्त्तते ॥

Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.