side effect
Americannoun
-
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.
-
any accompanying or consequential and usually detrimental effect.
the side effects of air pollution.
noun
-
any unwanted nontherapeutic effect caused by a drug Compare aftereffect
-
any secondary effect, esp an undesirable one
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.
About 44% of users in the study mentioned at least one side effect, most commonly gastrointestinal problems.
From Science Daily • May 24, 2026
Dandruff is a side effect of my medications, so I now use the same Head & Shoulders conditioner as my dad, which doesn’t help the middle-aged-man concern.
From Slate • May 23, 2026
But there’s also a quieter side effect I’ve come to love.
From Salon • May 12, 2026
The Wall Street Journal talked to Tanner about premium chocolate, dealmaking and how the company can help tackle “Ozempic breath”—a not-so-savory side effect some people experience with weight loss medications.
From The Wall Street Journal • Apr. 30, 2026
“In small doses, it has a mild, calming effect and improves the mood. The only side effect is some slight dizziness. We administer it to members of our community who have trouble keeping the peace.”
From "Insurgent" by Veronica Roth
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.
