Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
de-, dis-, dys- (prefixes)
These three affixes have essentially negative meanings involving stopping, separating, contracting, and the like. Decontaminate means “to take away or remove a contaminant”; deduce means literally “to lead away from”; depend, literally “to hang down”; decipher, literally “to reverse or undo”; deplane, “to get off a plane”; denominate, literally “to derive from a nominal.” De- can also combine to mean “completely,” “wholly,” as in defunct. Dis- can combine to mean “to stop” (discontinue), “to undo” (disprove), “to deprive of” (disarm), “an absence of” (disagreement), “not” (disappear), and the like. Dys- in combination can mean “bad” (dysphoric), “abnormal” (dysgenic), “nonfunctional” (dysfunctional), “impaired” (dyslexic), and the like.
