2.4.83 नाव्ययीभावादतोऽम्त्वपञ्चम्याः

Word by word (padaccheda)

Indeclinable न avyayaLeft context pañcamī · ekavacanaLeft context अतः pañcamī · ekavacanaSubstitute / term अम् prathamā · ekavacanaIndeclinable तु avyayaTarget अ- पञ्चम्याः ṣaṣṭhī · ekavacana

Indeclinable An avyaya such as च "and", वा "optionally", न "not".
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.
Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).

Dotted words are technical terms, dashed ones pratyāhāras (names for classes of sounds or affixes). Hover or tap one to see its card.

Full reading

न अतः अम् तु अ-पञ्चम्याः

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

Commentary

There is not लुक् elision of the case-affix after an अव्ययीभाव compound that ends in अ ; आम् is the substitute of its case-affix es, but not when it is the 5th case-affix.
This debars luk-elision which was to have taken place by the last sutra instead of luk-elision, we have आम् added to the words ending in short अ; for examples of this, see sutra 2.1.6; as उपकुम्भं तिष्ठति 'upakumbha is standing'; उपकुम्भं पश्य 'see the upakumbha.'

Why do we say 'after words ending in short अ'? Because after Avyayibhava compound ending in any other vowels there is not substitution, but there is total-elision of the case-affixes; as अधिस्त्री, अधिकुमारी.

But the ablative case-affix is not elided after Avyayibhava compound ending in short अ, nor is there the अम् substitution; as उपकुम्भादानय.

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