8.3.107
सुञः
Operational rule vidhi
In the छन्दस् (Vedas), ष् is substituted for the स् of the particle सु when preceded by a word having in it the change-effecting letter इ etc.
Word by word (padaccheda)
Target सुञः ṣaṣṭhī · ekavacana
- Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
Full reading
सुञः
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
Commentary
In the छन्दस् (Vedas), ष् is substituted for the स् of the particle सु when preceded by a word having in it the change-effecting letter इ etc.
Thus अभी षु णः सखीनाम् (Rig. IV. 31.3) ऊर्द्धं ऊ षु णः (Rig. I.36.13). The lengthening takes place by 6.3.134, and न changed to ण by 8.4.27.
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.