इणो यण्

Operational rule vidhi

The verb root इण् gets a यणादेश when followed by an अच् letter.

Word by word (padaccheda)

Target इणः ṣaṣṭhī · ekavacanaSubstitute / term prathamā · 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.

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

इणः

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)

इणः →

Replace iṇaḥ with yaṇ. Inherited words (anuvṛtti) may add further conditions.

Commentary

For the इ of the root इण् (एति) is substituted a semi-vowel (य) before the affix beginning with a vowel.
Thus यन्ति, यन्तु, आयन् ॥ This supersedes इयङ् substitution, and is itself superseded by 7.2.115, and 7.3.84 which ordain Vriddhi and Guna: on the maxim मध्येऽपवादाः पूर्वान् विधीन् बाधन्ते, नोत्तरात् ॥ "Apavadas that are surrounded by the rules which teach operations that have to be superseded by the apavada operations, supersede only those rules that precede, not those that follow them." So we have अयनम् and आयकः ॥

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