इकः काशे

Operational rule vidhi

A preposition ending in इ or उ lengthens its final before काश.

Word by word (padaccheda)

Target ṣaṣṭhī · ekavacanaRight context काशे saptamī · ekavacana

Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
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

काशे

Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.

Commentary

A preposition ending in इ or उ lengthens its final before काश।
As नीकाशः, वीकाशः, अनूकाशः ॥ काश is formed by अच् 3.1.134. Why do we say 'ending in इ or उ'? Observe प्रकाशः where the Preposition does not end in इक् ॥

Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.