अभ्यासस्यासवर्णे

Operational rule vidhi

An इवर्ण and an उवर्ण occurring at end of an अभ्यास respectively get इयङ् and उवङ् आदेश when followed by an असवर्ण letter.

Word by word (padaccheda)

Target ṣaṣṭhī · ekavacanaRight context असवर्णे 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

असवर्णे

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

Commentary

इवङ् and उवङ् are substituted for the इ and उ of a reduplicate, before a non-homogeneous vowel.
Thus इयेष, उवोष, इयर्त्ति, 7.4.77 but ईषतुः and ईषुः, ऊषतुः and ऊषुः before homogenous vowels and इयाय and उवाय before a non-vowel.

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