Integral

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mid 16th century: from late Latin integralis, from integer ‘whole’ (see integer). Compare with integrate and integrity.

wiktionary

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Borrowed from Middle French integral, from Medieval Latin integrālis, from Latin integer(“entire”); see integer.

etymonline

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integral (adj.)

late 15c., "of or pertaining to a whole; intrinsic, belonging as a part to a whole," from Old French intégral (14c.), from Medieval Latin integralis "forming a whole," from Latin integer "whole" (see integer). Related: Integrally. As a noun, 1610s, from the adjective.