side effect

noun

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.

any accompanying or consequential and usually detrimental effect:

the side effects of air pollution.

Also, side-effect.

Origin

1880-85

British Dictionary definitions for side-effects

noun

any unwanted nontherapeutic effect caused by a drug Compare aftereffect (sense 2)

any secondary effect, esp an undesirable one

Word Origin and History for side-effects

also side-effect, 1884, from side (adj.) + effect (n.). Medical use, with reference to drugs, is recorded from 1939.

side-effects in Medicine

side effect n.
A peripheral or secondary effect, especially an undesirable secondary effect of a drug or therapeutic regimen.