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

And as the drugs get more popular, the list of potential side effects is growing longer. —Jamie Ducharme, TIME, 4 Nov. 2024

However, the company decided not to advance this formulation to a late stage trial due to a high rate of side effects. —Bruce Gil, Quartz, 29 Oct. 2024

The drugs have been shown to help people with obesity lose up to 15 percent of their body weight, but come with side effects that mean many struggle to stay on the drugs for long—and weight regain is common for patients who come off the medication. —Thomas G. Moukawsher, Newsweek, 5 Nov. 2024

Is Taurine Safe? Supplemental taurine is considered very safe and isn't associated with adverse side effects, even when taken in high doses for long periods. —Jillian Kubala, Rd, Health, 5 Nov. 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