संज्ञोऽन्यतरस्यां कर्मणि

Operational rule vidhi

After the verb सम्-ज्ञः , the 3rd case-affix is optionally used in denoting the object.

Word by word (padaccheda)

Target संज्ञः ṣaṣṭhī · ekavacanaRight context अन्यतरस्याम् saptamī · ekavacanaRight context कर्मणि saptamī · ekavacana

Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
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").

Full reading

संज्ञः अन्यतरस्याम् कर्मणि

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

Commentary

After the verb सम्-ज्ञः , the 3rd case-affix is optionally used in denoting the object.
पित्रा or पितरं संजानीते 'he knows his father.' मात्रा or मातरं संजानीते ॥

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