side effect


Definition of side effect

: a secondary and usually adverse effect (as of a drug) toxic side effects

called also side reaction

Examples of side effect in a Sentence

Nausea and diarrhea are the side effects of the drug. the harmful side effects of using chemicals to kill insects The merger created positive side effects for both companies.
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Recent Examples on the Web Some users reported negative side effects of the drug. Peter Andreas, Time, "How Methamphetamine Became a Key Part of Nazi Military Strategy," 7 Jan. 2020 The autopsy report concluded that the cause of death was bronchial pneumonia with a side effect of diabetes mellitus, Mahoney said. Shari Rudavsky, Indianapolis Star, "Jeremy Crawford couldn't afford his high-priced insulin. That contributed to his death.," 29 Dec. 2019 The psychotic side effects of marijuana are used to bolster arguments on both sides of the legalization debate. Jayne O'donnell, USA TODAY, "Is marijuana linked to psychosis, schizophrenia? It's contentious but doctors, feds say yes," 15 Dec. 2019 The cut has the happy side effect of emphasizing her perfectly curated jewelry selection, an assortment of layered gold necklaces and hoops of varying sizes. Emily Dixon, Marie Claire, "Ashley Benson Completed Her Hair Transformation With a Short, Choppy Bob," 3 Dec. 2019 The side effects of obesity may be tied to continually lower life expectancy in the US. Scottie Andrew, CNN, "Americans weigh more this decade, but fewer adults want to lose weight," 28 Nov. 2019 What happened to the Lake Avenue tenants is just one example of what city officials and social-service organizations say is a growing problem: low-income residents suffering the side effects of a booming housing market. Jordyn Grzelewski, cleveland, "Closed Doors: Lakewood among booming housing markets where low-income renters are pushed out," 24 Nov. 2019 Johnson, a tight end from Columbia, Mo., pointed out the side effects of the rough stretch. Tom Murphy, Arkansas Online, "SEC wasteland: Hogs’ league futility mark 1 loss away," 23 Nov. 2019 My brother is seriously ill, fighting some unfortunate side effects of chemotherapy. Bulletin Board, Twin Cities, "Sunday Bulletin Board: The Case of Mama Hen and the Mongrel Chicks — or: What Would Jesus Say?," 10 Nov. 2019

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

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First Known Use of side effect

1814, in the meaning defined above

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Time Traveler for side effect

Time Traveler

The first known use of side effect was in 1814

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Statistics for side effect

Last Updated

17 Jan 2020

Cite this Entry

“Side effect.” The Dictionary, Merriam-Webster Inc., Accessed 23 January 2020.

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More Definitions for side effect

side effect


English Language Learners Definition of side effect

: an often harmful and unwanted effect of a drug or chemical that occurs along with the desired effect
: a result of an action that is not expected or intended

side effect


Medical Definition of side effect

: a secondary and usually adverse effect (as of a drug) toxic side effects a side effect of drowsiness caused by antihistamines

called also side reaction

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Comments on side effect

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


out of the ordinary or unreasonable

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