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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Nausea While mild, nausea is another potential side effect of taking melatonin supplements. Jennifer Lefton, Verywell Health, 23 May 2025 Over the past few weeks, TikTok users have sparked a heated conversation over a potential side effect of Dior Addict Lip Glow Oil. Jasmine Browley, Allure, 22 May 2025 And the drug can also bring unpleasant side effects like belly pain, nausea, diarrhea, and low-grade fever. Erica Sloan, SELF, 21 May 2025 Other cases may stem from hormone changes, infections, medication side effects, substance use, or underlying health conditions.1 Hormonal Changes Hormonal shifts, like those that happen during your period, pregnancy, or menopause, can leave you feeling run down. Brandi Jones, Health, 20 May 2025 See All Example Sentences for side effect

Word History

First Known Use

1814, in the meaning defined above

Time Traveler
The first known use of side effect was in 1814

Browse Nearby Words

Cite this Entry

“Side effect.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/side%20effect. Accessed 29 May. 2025.

Kids Definition

side effect

noun
: an often harmful and unwanted effect (as of a drug) that occurs along with the basic desired effect
the environmental side effects of using chemicals to kill pests

Medical Definition

side effect

noun
: 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

Last Updated: - Updated example sentences
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