वृद्भ्यः स्यसनोः

Operational rule vidhi

After the verbs वृत् 'to exist' etc., परस्मैपद is optionally used when the affixes स्य (Future and conditional) and सन् (Desiderative) follow.

Word by word (padaccheda)

Left context वृद्भ्यः pañcamī · bahuvacanaRight context स्य- सनोः saptamī · dvivacana

Left context Pañcamī (5th case): "after X", the operation applies to what follows (1.1.67 तस्मादित्युत्तरस्य). Also used for limits and sources.
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").

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Full reading

वृद्भ्यः स्य-सनोः

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

Commentary

After the verbs वृत् 'to exist' etc., परस्मैपद is optionally used when the affixes स्य (Future and conditional) and सन् (Desiderative) follow.
The वृतादि verbs are five in number and are included in the द्युतादि sub-class. They are वृत् to be, वृध् to grow, शृधू to fart or break wind; स्यन्दु to ooze, and कृपु to be able. As Ist Future वर्त्स्यति or वर्त्तिष्यते, it will be; conditional अवर्त्स्यत् or अवर्तिष्यत्; Desiderative विवृत्सति or विवर्त्तिषते &c.

In other tenses than the above, they are always Atmanepadi. As वर्त्तते it is.

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