prefix meaning "bad, ill, abnormal," from Gk. dys- "bad, hard, unlucky," from PIE base *dus- "bad, ill, evil" (cf. Skt. dus-, O.Pers. duš- "ill," O.H.G. zur-, Goth. tuz- "un-"), used as a prefix, a derivative of *deu- "to lack, be wanting" (cf. Gk. dein "to lack, want").