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

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

Some people experience no side effects, while others may experience side effects for a few months until their body adjusts to the IUD. —Lindsay Curtis, Verywell Health, 5 Nov. 2024

Even better, the pill was well tolerated with only mild side effects, and patients continuing treatment were seeing further weight loss. —Jesse Pound,samantha Subin, CNBC, 3 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