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-il Adjective-forming suffix indicating a relation.

From Latin -ilis. From Proto-Italic *-īlis 'id.' From Proto-Indo-European *-i̯h2-li̯- 'id.' An i-stem with an adjectival extension.

Romance: Western Vulgar Latin: Asturian -il, Portuguese -il, Galician -il, Catalan -il, French -ile, Italian -ile; Eastern Vulgar Latin: Aromanian -ilji, Romanian -il