तुमर्थाच्च भाववचनात्

Operational rule vidhi

The 4th case-affix is used after a crude-form which ends in an affix denoting 'condition' (abstract noun -- भाववचनाश्च (3.3.11)) and having the force of the affix तुम् (or Infinitive or purpose).

Word by word (padaccheda)

Left context तुम्- अर्थात् pañcamī · ekavacanaIndeclinable च avyayaLeft context भाववचनात् pañcamī · ekavacana

Left context Pañcamī (5th case): "after X", the operation applies to what follows (1.1.67 तस्मादित्युत्तरस्य). Also used for limits and sources.
Indeclinable An avyaya such as च "and", वा "optionally", न "not".

Full reading

तुम्-अर्थात् च भाववचनात्

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

Commentary

The 4th case-affix is used after a crude-form which ends in an affix denoting 'condition' (abstract noun -- भाववचनाश्च 3.3.11) and having the force of the affix तुम् (or Infinitive or purpose).
Ex. यागाय व्रजति 'he goes to offer a sacrifice' = यष्टुं व्रजति. So also त्यागाय व्रजति, भूतये व्रजति.

The word तुमर्थ means 'having the same significance as the affix तुम्.'

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