8.2.37
एकाचो बशो भष् झषन्तस्य स्ध्वोः
Operational rule vidhi
A बश्-वर्ण of an एकाच् and झषन्त part of a verb is converted to a भष् वर्ण - (1) in presence of a सकार, (2) in presence of a the word ध्व, or (3) at end of a पद
Word by word (padaccheda)
Target एकाचः ṣaṣṭhī · ekavacanaTarget ṣaṣṭhī · ekavacanaSubstitute / term prathamā · ekavacanaTarget झषन्तस्य ṣaṣṭhī · ekavacanaRight context स्ध्वोः saptamī · dvivacana
- 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.
- 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").
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
एकाचः झषन्तस्य स्ध्वोः
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
एकाचः झषन्तस्य → / स्ध्वोः
Replace ekācaḥ baśaḥ jhaṣantasya with bhaṣ when sdhvoḥ follows. Inherited words (anuvṛtti) may add further conditions.
Commentary
For the letters 1. ब 2. ग 3. ड or 4. द in the beginning of a mono-syllable and belonging to a root, and which ends in 1. झ 2. भ 3. घ 4. ढ or 5. ध there is substituted 1. भ 2. घ 3. ढ or 4. ध respectively before स् or ध्व or at the end of a word.
Thus from बुध् - भोत्स्यन्ते, अभुध्वम् and अर्थभुत्; from गुह् - नि घोक्ष्यते न्यघुढ्वम्, पर्णघुट् ॥ गुह् becomes गुढ् by 8.2.31, and thus it is a root ending in, jhash. From दुह् - (which becomes दुघ् by 8.2.32, and thus is a jhash ending root) धोक्ष्यते, अदुग्ध्वम्, गोधुक् ॥
So also from गृध् we have अजर्घाः the 2nd Person Singular Imperfect (लङ्) Intensive (yan luk). There is guna of ऋ, the स् (of सिप् 2nd Person Singular) is elided 6.1.68, and we have अजर्गर्ध्, and for the letter ग of the monosyllabic root, घ is substituted by the present aphorism. अजर्घर्ध् ॥ Then the final ध् is changed to द्, अजर्घर्द् 8.2.39. Then द् is changed to र् by 8.2.75. अजर्घर्र् ॥ Then the first र् is elided अजर्घर् 8.3.14. Then there is lengthening by 6.3.111, and we have अजर्घाः ॥
The monosyllable should be such that it should begin with a षश् and end with a झष् letter, and should be a full root or the portion (अवयव) of a root. In fact, this word which we found necessary in 8.2.32, is absolutely necessary here, in order to explain forms like गर्धप् from the Denominative root गर्दभय, by former क्विप् ॥
Why do we say "a monosyllable beginning with बश् and ending with झष् ?" Observe दामलिट् from the Denominative root दामलिह्म ॥ For had एकाचः not been employed in the sutra, the word धातोः 8.2.32 would have qualified बशः and the sutra would have meant "in a root which ended in a jhash, and which contained a बश् letter as its member; there is jhash substitution for such बश्", and the द of दामलिह would be changed then.
Why do we say "for a बश् letter"? Observe क्रुध् — क्रोत्स्यति here क is not changed to ष ॥ Why do we say ending in jhash? Observe दास्यति ॥ Why before स and ध्व? Observe बोद्धा, बोद्धुम्, बोद्धव्यम् ॥
Why have we taken ध्व and not merely ध? Observe दादद्धि from दध् in the यङ् लुक्, Imperative 2nd Person singular, the हि being changed to धि 6.4.101. The substitutes are four भ, घ, ड and ध, and their respective sthanins are also four, i. e. ब, ग, ड and द; so that ढ is the substitute of ड; but, as a matter of fact, ड never so stands at the beginning of a monosyllable, and so there is no ढ substitution.
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.