side effect

American  

Or side-effect

noun

1. any effect of a drug, chemical, or other medicine that is in addition to its intended effect, especially an effect that is harmful or unpleasant.

2. any accompanying or consequential and usually detrimental effect.

   the side effects of air pollution.

---

side effect British  

noun

1. any unwanted nontherapeutic effect caused by a drug Compare aftereffect

2. any secondary effect, esp an undesirable one

---

Etymology

Origin of side effect

First recorded in 1880–85

Example Sentences

The approach has not yet been tested in humans, and future studies will need to examine possible side effects as well as strategies for safely removing the bacteria after treatment.

From Science Daily

Perhaps he causes such extensive mayhem because he is the unintended side effect of a cataclysmic experiment.

From Salon

Previous research by the same team identified two main reasons patients stop taking these medications: cost or lack of insurance coverage, and side effects.

From Science Daily

Higher doses of GLP-1 medications are more effective, meaning people lose more weight than on lower doses, though the higher doses can come with more side effects.

From MarketWatch

Drugs designed to interfere with this process are less likely to cause harmful side effects.

From Science Daily

Related Words

• aftereffect
• reaction