इदोऽय् पुंसि

Operational rule vidhi

In पुंलिङ्ग, the 'इद्' part of the word 'इदम्' is converted to 'अय्' when followed by the सुँ-प्रत्यय.

Word by word (padaccheda)

Target इदः ṣaṣṭhī · ekavacanaSubstitute / term अय् prathamā · ekavacanaRight context पुंसि saptamī · ekavacana

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

Dotted words are technical terms. Hover or tap one to see its card.

Full reading

इदः अय् पुंसि

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)

इदः → अय् / पुंसि

Replace idaḥ with ay when puṃsi follows. Inherited words (anuvṛtti) may add further conditions.

Commentary

अय् is substituted for the इद् of इदम् in the Nominative 1st-Case singular masculine.
As अयम् ॥ In the Feminine इयम् ॥ As अयं ब्राह्मणः, and इयं ब्राह्मणी ॥

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