6.4.34
शास इदङ्हलोः
Operational rule vidhi
Before the Aorist in अङ् and before an affix beginning with a consonant having an indicatory क् or ङ् there is the substitution of ई for the vowel of शास्.
Word by word (padaccheda)
Target शासः ṣaṣṭhī · ekavacanaSubstitute / term prathamā · ekavacanaRight context अङ्- 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
शासः अङ्-
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
शासः → / अङ्-
Replace śāsaḥ with it when aṅ-haloḥ follows. Inherited words (anuvṛtti) may add further conditions.
Commentary
Before the Aorist in अङ् and before an affix beginning with a consonant having an indicatory क् or ङ् there is the substitution of ई for the vowel of शास्।
Thus अन्वशिषत्, अन्वशिषताम् and अन्वशिषन्; so also शिष्टः (with क्त), शिष्टवान् (with क्तवतु), तौ शिष्टः वयं शिष्मः (with the tense-affixes तः and मः which are ङित् by 1.2.4). The स is changed to ष by 8.3.60. Why do we say 'before the affixes of अ Aorist and consonant affixes'? Observe शासति, शशासतु, शशासुः ॥
Vart:- There is the substitution of इ for the vowel of शास् before the affix क्वि ॥ As आर्यशीः = आर्यान् शास्ति ॥ So also मित्रशीः ॥ The form is thus evolved, शास् + क्वि = शिस् + ० = शिर + ० = शीः (the short इ being lengthened by 8.2.76).
The root शास् is that root which takes अङ् aorist; namely the second Adadi शास् (शासु अनुशिष्टौ), and not the Bhvadi and the first Adadi शास (आङ शासु इच्छायाम्) Therefore not here आशास्ते, आशास्यमानः ॥
Vart:- But before क्विप्, this शास् also is changed, as आशीः, आशिषौ, आशिषः ॥ Or this is an irregular form indicated by the author in the word क्षियाशीः used in 8.2.104.
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.