7.3.31
यथातथयथापुरयोः पर्यायेण
Operational rule vidhi
Before a तद्धित affix having an indicatory ञ् , ण् or क् , the words यथातथ and यथापुर may have वृद्धि of the first vowel of their first member or that of the second member, in alteration.
Word by word (padaccheda)
Target यथातथयथापुरयोः ṣaṣṭhī · dvivacanaWith / by पर्यायेण tṛtīyā · ekavacana
- Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
- With / by Tṛtīyā (3rd case): accompaniment or means.
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
यथातथयथापुरयोः पर्यायेण
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
Commentary
Before a तद्धित affix having an indicatory ञ् , ण् or क् , the words यथातथ and यथापुर may have वृद्धि of the first vowel of their first member or that of the second member, in alteration.
That is, when the Negative particle gets the vriddhi, the words remain unchanged; and when these words are vriddhied, the negative particle remains unaltered. As आयथातथ्यम् or अयाथातथ्यम्, आयथापुर्यम् or अयाथापुर्यम् ॥ The words अयथातथ and अयथापुर should be considered to belong, as negative compounds, to Brahmanadi class 5.1.124: and take ष्यञ् ॥ In the sutra the compounds यथातथ and यथापुर are exhibited and are Avyayibhavas 2.1.7, and being neuters, the आ of तथा and पुरा are shortened. According to Patanjali this sutra is superfluous. When the negative particle takes Vriddhi, the compound should be analysed as, न यथातथा = अयथातथा, अयथातथा भावः = आयथातथ्यम् ॥ When the second member gets the vriddhi, the compound should be analysed as, यथातथा भावः = याथातथ्यं, न याथातथ्यम् = अयाथातथ्यम् ॥
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.