गौः सादसादिसारथिषु

Operational rule vidhi

The word गो retains its accent before 1. साद 2. सादि and 3. सारथि.

Word by word (padaccheda)

Substitute / term गौः prathamā · ekavacanaRight context साद- सादिसारथिषु saptamī · bahuvacana

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

गौः साद-सादिसारथिषु

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

Commentary

The word गो retains its accent before 1. साद 2. सादि and 3. सारथि।
Thus गोःसादः or गां सादयति = गो꣡सादः, गोः सादिः गो꣡ सादिः, and गो꣡ सारथिः ॥ साद is formed from सद् with the affix घञ् and forms a Genitive compound (गोः सादः). Or from the causative verb सादयति, we get गोसादः by adding अण् 3.9.1 गोसादी is formed by णिनि from the same causative root. The Krit-accent is debarred in the case of साद and सादिन्, the Samasa-accent 6.1.223 in the case of सारथि ॥

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