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

Some medical professionals have expressed concerns taking THC with antibiotics could increase the risk of unpleasant side effects of both. —Tribune Content Agency, The Mercury News, 30 Sep. 2024

Researchers are optimistic patients might stick with this medication longer than existing drugs, which patients often quit due to side effects. —Ken Alltucker, USA TODAY, 27 Sep. 2024

This trial also found the rate of side effects similar for Dupixent and the placebo. —Lisa Rapaport, EverydayHealth.com, 27 Sep. 2024

And volunteers given infusions of the antibody suffered from far more side effects such as nausea and headaches than those in a placebo group who received sham infusions. —science.org, 26 Sep. 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