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

This can increase the risk of side effects such as constipation, dizziness, dry mouth, and sleepiness.16 5. —Emmanuella Ogbonna, Health, 30 Dec. 2024

Here's what to expect—including benefits, potential side effects, and what to do in social situations. —Danielle Sinay, Glamour, 27 Dec. 2024

For many, the discomfort of side effects or the challenge of maintaining the regimen pushes them back to square one. —Josh Hammer, Newsweek, 23 Dec. 2024

It was banned in much of the world in the mid-1980s, due to concerns about these adverse side effects and its addictive potential. —Richard Windsor, theweek, 19 Dec. 2024

Word History

First Known Use

1814, in the meaning defined above

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