वाऽम्शसोः

Operational rule vidhi

The word 'स्त्री' gets an इयङ्-आदेश optionally when followed by अम् प्रत्यय or शस् प्रत्यय.

Word by word (padaccheda)

Indeclinable वा avyayaRight context अम्- शसोः saptamī · dvivacana

Indeclinable An avyaya such as च "and", वा "optionally", न "not".
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

वा अम्-शसोः

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

Commentary

The substitution of इवङ् for the ई of स्त्री is optional before the Accusative -2nd case-endings अम् and शस् (अस्).
Thus स्त्रीं पश्य or स्त्रियं पश्य, स्त्रीः पश्य or स्त्रियः पश्यः ॥

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