5.4.141
वयसि दन्तस्य दतृ
Operational rule vidhi
For दन्त is substituted दत् in a बहुव्रीहि समास when a numeral or सु precedes it and the whole word expresses a stage of life i.e. an age.
Word by word (padaccheda)
Right context वयसि saptamī · ekavacanaTarget दन्तस्य ṣaṣṭhī · ekavacanaWord दतृ
- 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").
- Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
- Word Case not marked in the source data.
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Full reading
वयसि दन्तस्य दतृ
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
Commentary
For दन्त is substituted दत् in a बहुव्रीहि समास when a numeral or सु precedes it and the whole word expresses a stage of life i.e. an age.
The ऋ of दतृ is indicatory, making Rule 7.1.70 applicable, by which a nasal is added before त् in declining these words in sarvanamasthana cases: and rule 4.1.6 also applies to them. All rules relating to उगित् apply to these. Thus द्वौ दन्तावस्य = द्विदन् "a child of the age in which two teeth have appeared". So also त्रिदन्, चतुर्दन् ॥ शोभनादन्ता अस्य समस्ता जाताः = सुदन् कुमारः "a boy of the age in which all his teeth have appeared beautifully". Why do we say denoting 'age'? Observe द्विदन्तः कुंजरः ॥
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.