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definitions

dys-

  1. a combining form meaning “ill,” “bad,” used in the formation of compound words: dysfunction.

Origin of dys-

< Greek; cognate with Old Norse tor-, German zer-, Sanskrit dus-
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for dys-

dys-

prefix
  1. diseased, abnormal, or faultydysentery; dyslexia
  2. difficult or painfuldysuria
  3. unfavourable or baddyslogistic

Word Origin for dys-

via Latin from Greek dus-
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for dys-

word-forming element meaning "bad, ill, abnormal," from Greek dys-, inseparable prefix "destroying the good sense of a word or increasing its bad sense" [Liddell and Scott], "bad, hard, unlucky," from PIE root (and prefix) *dus- "bad, ill, evil" (cf. Sanskrit dus-, Old Persian duš- "ill," Old English to-, Old High German zur-, Gothic tuz- "un-"), a derivative of *deu- "to lack, be wanting" (cf. Greek dein "to lack, want").

Very productive in ancient Greek, where it could attach even to proper names (e.g. dysparis "unhappy Paris"); its entries take up nine columns in Liddell and Scott. Among the words formed from it were some English might covet: dysouristos "fatally favorable, driven by a too-favorable wind;" dysadelphos "unhappy in one's brothers;" dysagres "unlucky in fishing;" dysantiblepos "hard to look in the face."

Online Etymology Dictionary, © 2010 Douglas Harper
dys- in Medicine

dys-

pref.
  1. Abnormal:dysplasia.
  2. Impaired:dysesthesia.
  3. Difficult:dysphonia.
  4. Bad:dyspepsia.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.