indeclinable adverb
Analysis. kad- (interrogative stem, "who/what") + āci (temporal suffix forming indefinite adverbs); literally "at what time", used indefinitely to mean "at some time" or "sometimes".
Etymology. kad- is the interrogative stem related to Sanskrit ka- ("who, what") and ultimately to Indo-European *kwo-/kwi- (English who, what; Latin quod, quis; Greek pós, tís). The suffix -āci is an old temporal locative formation (compare Vedic kádā "when", Sanskrit kadā); the -ci is an enclitic particle of indefiniteness (related to cid, meaning "any"). Together they form an indefinite temporal expression: "at whatever time" → "sometimes, ever".
Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.
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