side effect
noun
: 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.
Recent Examples on the Web
Mild side effects, like headache, pain at the injection site, fever, and nausea, are common.13
The Pfizer Abrysvo and Moderna mResvia vaccines have been FDA-approved for high-risk adults under 50.
—
Stephanie Brown, Verywell Health, 4 Aug. 2025
Children can suffer side effects from common shots like the MMR vaccine, ranging from mild symptoms like a rash or fever to rare fatal complications.
—ArsTechnica, 4 Aug. 2025
Breast cancer treatment and side effects, including menopause Klimpl lives in San Diego but is a Hawaii native.
—David Oliver, USA Today, 31 July 2025
Consuming too much caffeine can also lead to side effects like anxiety, rapid heartbeat, agitation, and trouble sleeping.
—Jillian Kubala, Health, 31 July 2025
See All Example Sentences for side effect
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Stephanie Brown, Verywell Health, 4 Aug. 2025
Children can suffer side effects from common shots like the MMR vaccine, ranging from mild symptoms like a rash or fever to rare fatal complications.
—ArsTechnica, 4 Aug. 2025
Breast cancer treatment and side effects, including menopause Klimpl lives in San Diego but is a Hawaii native.
—David Oliver, USA Today, 31 July 2025
Consuming too much caffeine can also lead to side effects like anxiety, rapid heartbeat, agitation, and trouble sleeping.
—Jillian Kubala, Health, 31 July 2025
See All Example Sentences for side effect
Cite this Entry
“Side effect.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/side%20effect. Accessed 10 Aug. 2025.
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