Definitive

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late Middle English: from Old French definitif, -ive, from Latin definitivus, from definit- ‘set within limits’, from the verb definire (see define).

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From Middle French définitif.

etymonline

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definitive (adj.)

late 14c., "ending, determining, conclusive," from Old French definitif (12c.), from Latin definitivus "explanatory, definitive," in Late Latin "definite," from definit-, past-participle stem of definire "to limit, determine, explain," from de "completely" (see de-) + finire "to bound, limit," from finis "boundary, end" (see finish (v.)). As a noun, in grammar, "a defining or limiting word," by 1751. Related: Definitively; definitiveness.