चतुरनडुहोरामुदात्तः

Operational rule vidhi

The words चतुर् and अनडुह् get an उदात्तः आम्-आगम when followed by a सर्वनामस्थान.

Word by word (padaccheda)

Target चतुर्- अनडुहोः ṣaṣṭhī · dvivacanaSubstitute / term आम् prathamā · 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. Hover or tap one to see its card.

Full reading

चतुर्-अनडुहोः आम्

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)

चतुर्- अनडुहोः → आम्

Replace catur-anaḍuhoḥ with ām udāttaḥ. Inherited words (anuvṛtti) may add further conditions.

Commentary

चतुर् and अनडुह् get the acutely accented (उदात्त) augment आ (आम्) after the उ in the strong cases.
Thus चत्वा꣡रः, अनड्वा꣡न्, अनड्वा꣡हौ, अनड्वा꣡हः, अनड्वा꣡हम् ॥ The rule applies to compounds ending with चत्वार् and अनडुह्, as प्रियचत्वार्, प्रियचत्वारौ, प्रियचत्वारः, प्रियानड्वान्, प्रियानड्वाहौ, प्रियानड्वाहः ॥

Vart:- In the case of अनडुह् there is option in the feminine, as, अनडुही, or अनड्वाही ॥ This would be so, because it occurs in Gauradi class 4.1.41.

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