8.4.63
शश्छोऽटि
Operational rule vidhi
A शकार sandwiched between a झय् letter on the left and an अट् letter on the right is optionally converted to a छकार.
Word by word (padaccheda)
Target शः ṣaṣṭhī · ekavacanaSubstitute / term छः prathamā · ekavacanaRight context saptamī · 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.
- 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
शः छः
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
शः → छः /
Replace śaḥ with chaḥ when aṭi follows. Inherited words (anuvṛtti) may add further conditions.
Commentary
in the room of श preceded by a surd Mute, there is optionally the letter छ् when a vowel or य, व or र follows such श।
Though झय् means all Mutes, the rule, however, applies to surd mutes. The words झय् and अन्यतरस्यां are to be read into the sutra. Thus वाक् + शेते = वाक्छेते or शेते ॥ अग्निचिच्छेते or अग्निचित् शेते, श्वलिट् शेते or छेते, त्रिष्टुप्छेते or शेते ॥
Vart:- It should rather be stated when a letter of the अम् pratyahara follows. The sutra only gives अट् letters, the vartika adds the letters ल, and the nasals. Thus तत् श्लोकेन = तच् छ्लोकेन, तच्छ्मश्रुणा ॥
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.