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 pandemic hit and had the nice side effect of uniting a group of my old high school friends, who had nothing better to do late on Saturday nights, for online video chats. Paul Eisenberg,, 9 May 2021 The data come from electronic diaries that clinical trial volunteers kept for seven days after each injection in order to record side effect. Theresa Machemer, Smithsonian Magazine, 5 May 2021 Overall, one in roughly 120,000 AstraZeneca shots has triggered the side effect in the country. Kai Kupferschmidt, Science | AAAS, 3 May 2021 The host addressed how Johnson & Johnson recalled its vaccine after finding a rare side effect in certain individuals that caused blood clots. Nick Romano,, 3 May 2021 During their review, health officials found that out of nearly 8 million people who received the vaccine, there were 15 patients, all of whom were women under the age of 60, who had experienced the side effect. Eliza Fawcett,, 26 Apr. 2021 In a statement, the agency stressed the importance of treating the potential side effect and issued guidelines to health care professionals on the lookout for the rare clotting disorder. New York Times, 20 Apr. 2021 In the statement, Cansino also explained that its vaccine targets a different vector than the AstraZeneca and J&J jabs and may therefore not induce the same side effect. Grady Mcgregor, Fortune, 19 Apr. 2021 The department said Monday anyone who received the vaccine more than three weeks ago shouldn’t fear the rare side effect. Christen Smith, Washington Examiner, 16 Apr. 2021

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

6 Jun 2021

Cite this Entry

“Side effect.” Dictionary, Merriam-Webster, Accessed 15 Jun. 2021.

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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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