side effect

or side-ef·fect

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

noun

1. any unwanted nontherapeutic effect caused by a drug Compare aftereffect
2. any secondary effect, esp an undesirable one

Word History and Origins

Origin of side effect¹

First recorded in 1880–85

Example Sentences

"Our findings highlight the importance of identifying patients with high-risk who are most likely to benefit from heart protection, and therefore, minimize unnecessary side effects and health care costs for low-risk people," Bonatto said.

From Science Daily

There were some mild side effects such as nausea and dizziness, but no serious ones, say the researchers.

From BBC

This approach is especially prominent in areas like cancer research where genetic profiling of tumors can lead to potentially better outcomes and fewer side effects.

From Science Daily

This knowledge can be used to develop drugs for chronic pain that are more effective and have fewer side effects.

From Science Daily

Participants experienced minor side effects from the treatment but none had serious adverse reactions.

From Science Daily

Related Words

• aftereffect
• reaction