विभाषाऽऽङि रुप्लुवोः

Operational rule vidhi

The affix घञ् is optionally used after the verbs 1. रू 'to roar' 2. प्लु 'to float' when the preposition अङ् is in composition.

Word by word (padaccheda)

Substitute / term prathamā · ekavacanaRight context आङि saptamī · ekavacanaTarget रु- प्लुवोः ṣaṣṭhī · 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").
Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).

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Full reading

आङि रु-प्लुवोः

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

As a rewrite rule (sketch from case endings)

रु- प्लुवोः → / आङि optional

Replace ru-pluvoḥ with vibhāṣā when āṅi follows, optionally. Inherited words (anuvṛtti) may add further conditions.

Commentary

The affix घञ् is optionally used after the verbs 1. रू 'to roar' 2. प्लु 'to float' when the preposition अङ् is in composition.
As आरावः or आरवः 'noise'; आप्लावः or आप्लवः 'bathing'.

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