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  1. injurious to health: deleterious gases.
  2. harmful; injurious: deleterious influences.
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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 formsdel·e·te·ri·ous·ly, adverbdel·e·te·ri·ous·ness, nounnon·del·e·te·ri·ous, adjectivenon·del·e·te·ri·ous·ly, adverbnon·del·e·te·ri·ous·ness, nounun·del·e·te·ri·ous, adjectiveun·del·e·te·ri·ous·ly, adverbun·del·e·te·ri·ous·ness, noun

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Antonyms for deleterious

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for deleterious

bad, destructive, detrimental, hurtful, injurious, mischievous, nocuous, pernicious, prejudicial, ruinous, nocent, ruining

Examples from the Web for deleterious

Contemporary Examples of deleterious

Historical Examples of deleterious

British Dictionary definitions for deleterious


  1. harmful; injurious; hurtful
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Derived Formsdeleteriously, adverbdeleteriousness, noun

Word Origin for deleterious

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

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.

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Online Etymology Dictionary, © 2010 Douglas Harper

deleterious in Medicine


  1. Having a harmful effect; injurious.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.