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[del-i-teer-ee-uh s] /ˌdɛl ɪˈtɪər i əs/
injurious to health:
deleterious gases.
harmful; injurious:
deleterious influences.
Origin of deleterious
1635-45; < Greek dēlētḗrios destructive, adj. derivative of dēlētḗr destroyer, equivalent to dēlē- variant stem of dēleîsthai to hurt, injure + -tēr agent suffix + -ios adj. suffix; see -ious
Related forms
deleteriously, adverb
deleteriousness, noun
nondeleterious, adjective
nondeleteriously, adverb
nondeleteriousness, noun
undeleterious, adjective
undeleteriously, adverb
undeleteriousness, noun
2. pernicious, hurtful, destructive; noxious.
2. beneficial. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for deleterious
  • But that's not to say that they couldn't have some deleterious health effects.
  • In animals, individuals who have suffered deleterious changes are removed by the process of natural selection.
  • The result: The deleterious insects emerged more pestilent and plentiful than ever.
  • That would have a deleterious effect on free speech, privacy advocates say.
  • There is little doubt that lack of coverage was deleterious to their health.
  • It is clearly having a deleterious effect on your cognition.
  • Higher taxes have an especially deleterious effect on growth.
  • Over time, this had a deleterious effect on quality.
  • Environmental advocates, too, worry about unforeseen deleterious effects on the ocean ecosystems near lime deposition points.
  • The chair seemed completely unconcerned about the deleterious consequences this one student might have on the rest of the class.
British Dictionary definitions for deleterious


harmful; injurious; hurtful
Derived Forms
deleteriously, adverb
deleteriousness, noun
Word Origin
C17: from New Latin dēlētērius, from Greek dēlētērios injurious, destructive, from dēleisthai to hurt
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
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Word Origin and History for deleterious

1640s, from Medieval Latin deleterius, from Greek deleterios "noxious," from deleter "destroyer," from deleisthai "to hurt, injure." Related: Deleteriously; deleteriousness.

Online Etymology Dictionary, © 2010 Douglas Harper
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deleterious in Medicine

deleterious del·e·te·ri·ous (děl'ĭ-tēr'ē-əs)
Having a harmful effect; injurious.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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