उष्ट्रः सादिवाम्योः

Operational rule vidhi

The word उष्ट्र retains its accent before सादि and वामि.

Word by word (padaccheda)

Substitute / term उष्ट्रः prathamā · ekavacanaRight context सादिवाम्योः saptamī · dvivacana

Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.
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").

Full reading

उष्ट्रः सादिवाम्योः

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

Commentary

The word उष्ट्र retains its accent before सादि and वामि।
Thus उ꣡ष्ट्रसादि and उ꣡ष्ट्रवामि ॥ The word उष्ट्र is derived from उप् by ष्ट्रन् affix (Unadi IV. 162) and has acute on the first 6.1.197. This is either a Karmadharaya or a Genitive compound. In some texts the above examples are given with a visarga in the masculine, and not Neuter.

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