स्रोतसो विभाषा ड्यड्ड्यौ

Operational rule vidhi

The affixes ड्यत् and ड्य come in the sense of 'what stays there' after the word स्रोतस् and before these affixes the final syllable अस् of स्रोतस् is elided, in the छन्दस् (Vedas).

Word by word (padaccheda)

Left context स्रोतसः pañcamī · ekavacanaSubstitute / term prathamā · ekavacanaSubstitute / term ड्यत्- ड्यौ prathamā · dvivacana

Left context Pañcamī (5th case): "after X", the operation applies to what follows (1.1.67 तस्मादित्युत्तरस्य). Also used for limits and sources.
Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.

Dotted words are technical terms. Hover or tap one to see its card.

Full reading

स्रोतसः ड्यत्-ड्यौ

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

Commentary

The affixes ड्यत् and ड्य come in the sense of 'what stays there' after the word स्रोतस् and before these affixes the final syllable अस् of स्रोतस् is elided, in the छन्दस् (Vedas).
This debars यत् which comes in the alternative. As स्रोतसि भवः = स्रोत्यः॑ or स्रोत्यः॒꣡ the difference being in the accent 3.1.3 and 6.1.185. The anubandha ड causes the elision of अस् of स्रोतस् ॥ When यत् is added the form is स्रोतस्यः॑ ॥

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