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.
Human testing will be essential to determine the molecule's actual side effect profile.
From Science Daily ● Nov. 4, 2026
Another side effect, he said, is that Claude and other AI systems could start to believe they deserve rights like humans.
From Los Angeles Times ● Nov. 2, 2026
While it is not caused by GLP-1 drugs directly, rapid weight loss can, for some people, come with a side effect of loose skin - including around the face.
From BBC ● Oct. 22, 2026
The other possibility is that the rise in living with parents is somehow a cause, not a side effect, of declining marriage and fertility.
From MarketWatch ● Sep. 22, 2026
Worry is yet another side effect of dying.
From "The Fault in Our Stars" by John Green
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