word-forming element meaning "before," from Old French pre- and Medieval Latin pre-, both from Latin prae (adverb and preposition) "before in time or place," from PIE *peri- (source also of Oscan prai, Umbrian pre, Sanskrit pare "thereupon," Greek parai "at," Gaulish are- "at, before," Lithuanian prie "at," Old Church Slavonic pri "at," Gothic faura, Old English fore "before"), extended form of root *per- (1) "forward," hence "beyond, in front of, before."
The Latin word was active in forming verbs. Also see prae-. Sometimes in Middle English muddled with words in pro- or per-.
late 14c., deffinen, diffinen, "to specify; to fix or establish authoritatively;" of words, phrases, etc., "state the signification of, explain what is meant by, describe in detail," from Old French defenir, definir "to finish, conclude, come to an end; bring to an end; define, determine with precision," and directly from Medieval Latin diffinire, definire, from Latin definire "to limit, determine, explain," from de "completely" (see de-) + finire "to bound, limit," from finis "boundary, end" (see finish (v.)). From c. 1400 as "determine, declare, or mark the limit of." Related: Defined; defining.
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Harper, D. (n.d.). Etymology of predefine. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/predefine