6.3.25
आनङ् ऋतो द्वन्द्वे
Operational rule vidhi
In a द्वन्द समास of words ending in the short ऋ and expressing relationship through study or blood, the आनङ् is the substitute of ऋ of the first member.
Word by word (padaccheda)
Substitute / term आनङ् prathamā · ekavacanaTarget ऋतः ṣaṣṭhī · ekavacanaRight context saptamī · ekavacana
- Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.
- 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").
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Full reading
आनङ् ऋतः
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
ऋतः → आनङ् /
Replace ṛtaḥ with ānaṅ when dvandve follows. Inherited words (anuvṛtti) may add further conditions.
Commentary
In a द्वन्द समास of words ending in the short ऋ and expressing relationship through study or blood, the आनङ् is the substitute of ऋ of the first member.
Thus होतापोतारौ, नेष्टोद्गातारौ, प्रशास्ताप्रतिहर्त्तारौ मातापितरौ, याताननान्दरौ ॥ The substitute is really आ, the न् is useful only to prevent the application of 1.1.51, by which a र comes after every simple vowel substitute of ऋ ॥
Why do we say 'both words ending in ऋ'? Observe पितृपितामहौ ॥ The anuvritti of पुत्र is understood here, so that the ऋ of the first member is changed to आ before पुत्र also, though it does not end in ऋ. As पितापुत्रौ, मातापुत्रौ ॥
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.