side effect
Americannoun
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side effects
plural
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any effect of a drug, chemical, or other medicine that is in addition to its intended effect, especially an effect that is harmful or unpleasant.
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any accompanying or consequential and usually detrimental effect.
the side effects of air pollution.
noun
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any unwanted nontherapeutic effect caused by a drug Compare aftereffect
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any secondary effect, esp an undesirable one
Other Word Forms
Noun Inflected Forms
Etymology
Origin of side effect
First recorded in 1880–85
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
“They would want there to be a credible association that they believe provides some basis for saying that there’s causation,” meaning evidence that the drug does, in fact, cause the side effect.
From The Wall Street Journal ● Sep. 19, 2026
Even beyond the black market, the glamorization of testosterone often glosses over the primary, life-altering side effect: reduced fertility.
From Slate ● Sep. 13, 2026
Taking multiple medications increases the opportunity for a side effect to be misinterpreted as a separate diagnosis.
From Science Daily ● Sep. 11, 2026
That’s an inevitable side effect of appearing on a Bill Lawrence show.
From Los Angeles Times ● Aug. 10, 2026
The Malaclaw’s bite has the unusual side effect of making the victim highly unlucky for a period of up to a week after the injury.
From "Fantastic Beasts and Where to Find Them" by J.K. Rowling
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
