del·​e·​te·​ri·​ous | \ ˌde-lə-ˈtir-ē-əs How to pronounce deleterious (audio) \

Definition of deleterious

: harmful often in a subtle or unexpected way deleterious effects deleterious to health

Keep scrolling for more

Other Words from deleterious

deleteriously adverb
deleteriousness noun

Choose the Right Synonym for deleterious

pernicious, baneful, noxious, deleterious, detrimental mean exceedingly harmful. pernicious implies irreparable harm done through evil or insidious corrupting or undermining. the claim that pornography has a pernicious effect on society baneful implies injury through poisoning or destroying. the baneful notion that discipline destroys creativity noxious applies to what is both offensive and injurious to the health of a body or mind. noxious chemical fumes deleterious applies to what has an often unsuspected harmful effect. a diet found to have deleterious effects detrimental implies obvious harmfulness to something specified. the detrimental effects of excessive drinking

Examples of deleterious in a Sentence

In developing countries, the imposition of boundaries around national parks and protected areas has been deleterious for both people and wildlife. — Kristin B. Gunther, Association of American Geographers, 2002 Most everyone now knows the action of pressing mouse keys is far more deleterious to the tender structures of the wrist and hand than typing is. — Michael Finley, Albany (New York) Times-Union, 2 Sept. 1998 This skewed allocation of resources away from those most in need, in turn, insures that many young people from low-income families will continue to be shut out of the economy, with obvious deleterious family and social consequences. — Iris C. Rotberg, Education Week, 9 Mar. 1994 For as James Keirans pointed out to me, ticks are the world's most notorious carriers of the agents of diseases that strike animals, wild and domestic. And they rank second only to mosquitoes in their deleterious effect on humans. — Edwards Park, Smithsonian, January 1987 The chemical is deleterious to the environment. The drug has no deleterious effects on patients.
See More

Recent Examples on the Web

In her new book Cribsheet, the economist Emily Oster writes that rumors of the deleterious effects of screen time have been greatly exaggerated. Laura Turner, Glamour, "The Big Problem With the New Screen Time Guidelines for Kids," 26 Apr. 2019 The customizable bedtime setting also tells the Forma when to bump up the orange light in the evening to prevent extra blue light from having a deleterious effect on your eyes and mind before sleep. Valentina Palladino, Ars Technica, "Kobo Forma review: A formidable opponent for Amazon’s Kindle Oasis," 22 Nov. 2018 Hippo poop is piling up in Tanzania’s freshwater fisheries—which is bad news for biodiversity, and deleterious for the dinnerplate. Jason G. Goldman, Scientific American, "Hippo Dung Fouls Up Freshwater Fisheries," 14 June 2018 Musk’s behavior this summer has compounded the deleterious effect of technical problems in late March and early April, including a deadly autopilot crash, a Model S recall and production target misses. Rani Molla, Recode, "Elon Musk’s summer of bad behavior hasn’t affected Tesla’s sales, but it has hurt its reputation," 10 Oct. 2018 Add to that the potentially deleterious effects of tariffs being levied by President Donald Trump, and 2018 is quite a challenging year for the family farming business. The Aegis, "Roller coaster ride [Editorial]," 13 July 2018 No government has ever before sought to impose such a sweeping privacy control, perhaps because of the obviously deleterious effects on law enforcement. Brian E. Finch And, WSJ, "The EU’s Gift to Cybercriminals," 28 May 2018 Reports have have been trickling in for weeks in about the deleterious effect the president’s economic aggression is having on American businesses, from pork producers to fuel cell manufacturers. Benjamin Hart, Daily Intelligencer, "Harley-Davidson Announces It Will Move Some Operations to Europe Amid Trade War," 25 June 2018 While there's no clear connection between Spade's and Bourdain's deaths, high-profile suicides could have a deleterious effect on people experiencing emotional or psychological hardships, potentially leading to a contagion effect. Julyssa Lopez, Glamour, "How to Spot Signs of Suicide—and What You Can Do to Help," 8 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'deleterious.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of deleterious

1643, in the meaning defined above

History and Etymology for deleterious

Greek dēlētērios, from dēleisthai to hurt

Keep scrolling for more

Learn More about deleterious

Listen to Our Podcast about deleterious

Dictionary Entries near deleterious



delete key





Statistics for deleterious

Last Updated

16 May 2019

Look-up Popularity

Time Traveler for deleterious

The first known use of deleterious was in 1643

See more words from the same year

Keep scrolling for more

More Definitions for deleterious



English Language Learners Definition of deleterious

formal : damaging or harmful


del·​e·​te·​ri·​ous | \ ˌdel-ə-ˈtir-ē-əs How to pronounce deleterious (audio) \

Medical Definition of deleterious

: harmful often in a subtle or an unexpected way the deleterious effects of radiation and chemotherapy on the marrow— Christine Gorman deleterious genes

Keep scrolling for more

Comments on deleterious

What made you want to look up deleterious? Please tell us where you read or heard it (including the quote, if possible).


showing courage and determination

Get Word of the Day daily email!

Test Your Vocabulary

Words for Summer: A Quiz

  • a closeup of a sunflower
  • Which of the following words means “of or relating to summer”?
True or False

Test your knowledge - and maybe learn something along the way.


Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!