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 The program also has the nice side effect of changing the overall approach to healthcare in a way that can improve the health of the community. Annalisa Merelli, Quartz, "How to fix the cash flow problem that makes rural healthcare unsustainable," 30 July 2020 That’s another side effect of the virus; tourism has stopped cold, so the city has been turned back to the locals. Carl Nolte,, "Without a tourist in sight, San Francisco is less lively," 27 June 2020 The interconnected crises gripping the country have had the side effect of, for the first time in his Presidency, forcing Trump off center stage. Eric Lach, The New Yorker, "Donald Trump Returns to a Changed Campaign Trail," 19 June 2020 Osman’s lack of productivity in November was a side effect of Cleveland’s messy offense. Cameron Fields, cleveland, "Cedi Osman didn’t have a steady role during the season, but had pockets of effectiveness: Cleveland Cavaliers Season Review," 8 July 2020 Blood clots in general are a potentially dangerous side effect of COVID-19 and have been found in numerous patients with coronavirus, though experts are still unsure why. Korin Miller,, "Man Suffers 4-Hour Erection From Blood Clots Due to Coronavirus," 2 July 2020 As San Francisco continues its start-stop efforts to reopen, planners at Muni are trying to stave off what could be a devastating side effect: epic traffic jams. Rachel Swan,, "Muni’s solution for a possible Carmageddon: Emergency transit-only lanes," 27 June 2020 For many people that is leading to an embarrassing and unpleasant side effect: blemishes, pimples, zits — or what dermatologists call acne. Sandee Lamotte, CNN, "'Maskne': Why your face is breaking out under your mask and how to stop it," 25 June 2020 An unfortunate side effect, however, is ankle chafing. Courtney Thompson, CNN Underscored, "20 must-have accessories for anyone with a Peloton," 25 June 2020

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

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The first known use of side effect was in 1814

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Last Updated

4 Aug 2020

Cite this Entry

“Side effect.” Dictionary, Merriam-Webster, Accessed 10 Aug. 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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