अकर्तर्यृणे पञ्चमी

Operational rule vidhi

A word implying 'debt', considered as a 'cause' but not as कर्तृ or agent, takes the 5th case-affix.

Word by word (padaccheda)

Right context अकर्तरि saptamī · ekavacanaRight context ऋणे saptamī · ekavacanaSubstitute / term पञ्चमी prathamā · ekavacana

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").
Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.

Full reading

अकर्तरि ऋणे पञ्चमी

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

Commentary

A word implying 'debt', considered as a 'cause' but not as कर्तृ or agent, takes the 5th case-affix.
Ex. शताद्बद्धः 'he has been bound on account of a debt of a hundred pieces.'

Why do we say 'when not denoting the agent ?' Observe शतेन बन्धितः; 'a debt of hundred has thrown him in prison'; here शत being considered as a prayojaka hetu, is an agent and takes the third case-affix.

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