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Definitions

side effect

NOUN
adverse or unwanted secondary effect
Synonyms
STRONGEST
aftereffect reaction
WEAK
aftermath aftertaste by-product carry-over concomitant corollary leftover offshoot secondary response side issue sidebar spinoff

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.

What will the next scan bring when it comes to a treatment, surgery, or side effect that means this healthy, happy moment was fleeting?

From Slate • May 6, 2026

The airplane fire threat is a side effect of the proliferation of cellphones, tablets and other electronic devices powered by rechargeable batteries.

From The Wall Street Journal • May 6, 2026

More recently, it’s become an off-label success story after doctors realized a side effect of taking the drug was hair growth.

From MarketWatch • Apr. 27, 2026

Mild-to-moderate injection site reactions were the most common side effect, but nearly all of these reactions resolved themselves within five days.

From Barron's • Apr. 20, 2026

“Nah, nostalgia is a side effect of dying,” he answered.

From "The Fault in Our Stars" by John Green