"in accordance or agreement with a certain standard, model, or original," 1670s, from French correct "right, proper," from Latin correctus, past participle of corrigere "to put straight; to reform" (see correct (v.)). Related: Correctly; correctness.
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from Proto-Germanic *in-assu- (cognates: Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, originally belonging to the noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).
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Harper, D. (n.d.). Etymology of correctness. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/correctness