side effect

noun

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

That’s why antibiotics can sometimes come with gastrointestinal side effects. Megan Thielking, STAT, "As drug resistance grows, combining antibiotics could turn up new treatments," 4 July 2018 At North Gwinnett High more than a decade ago, Holcomb saw friends broken by meth, a drug with awful side effects. Joshua Sharpe, ajc, "Meth, ‘the Devil’s drug,’ is back and killing more people than ever," 4 July 2018 Other patients get slower-acting or less effective pain pills, alternatives with more side effects or even sedation. Linda A. Johnson, chicagotribune.com, "The other opioid crisis: Hospitals grapple with prolonged injected opioid shortage," 28 June 2018 Other patients get slower-acting or less effective pain pills, alternatives with more side effects or even sedation. Washington Post, "US hospitals grapple with prolonged injected opioid shortage," 27 June 2018 But this is like a doctor writing out a prescription for an aggressive drug, with potentially negative side effects, without a long-term plan for the patient’s health. David M. Smick, WSJ, "Who Unraveled the New World Order?," 12 June 2018 For the past several years, cancer care has been evolving away from chemotherapy — older drugs with harsh side effects — in favor of gene-targeting therapies, hormone blockers and immune system treatments. Rick Jervis, USA TODAY, "Thousands of women could forgo chemotherapy for early-stage breast cancer, study says," 3 June 2018 Cancer care has been evolving away from chemotherapy — older drugs with harsh side effects — in favor of gene-targeting therapies, hormone blockers and immune system treatments. Marilynn Marchione, latimes.com, "Many breast cancer patients can skip chemo, study finds," 3 June 2018 Moving away from chemo Cancer care has been evolving away from chemotherapy -- older drugs with harsh side effects -- in favor of gene-targeting therapies, hormone blockers and immune system treatments. CBS News, "Many breast cancer patients can safely skip chemotherapy, major study finds," 3 June 2018

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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Last Updated

12 Sep 2018

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Time Traveler for side effect

The first known use of side effect was in 1814

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More Definitions for side effect

side effect

noun

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

noun

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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