副作用
ふくさよう
fukusayou
In a medical context, this term refers to the unintended and typically adverse reactions caused by a medication or treatment. It is most commonly paired with the verb 出る (deru - to appear/occur) or 抑える (osaeru - to suppress/minimize). While usually negative, some medical contexts may discuss "positive side effects," though these are rare in everyday conversation.
In a broader social or economic context, it describes the unintended negative consequences of a specific action, policy, or trend. It implies that while the primary goal was achieved, an unforeseen and undesirable secondary effect has emerged. In these cases, it is often used to describe systemic issues, such as the negative impact of rapid technological advancement or economic shifts.
Unlike the word 影響 (eikyou - influence/effect), which is neutral, 副作用 almost always carries a negative connotation, emphasizing the "cost" or "penalty" associated with a particular benefit.
Meanings
An unintended and usually harmful effect of a drug or medical treatment.
副作用が出る。
Side effects appear.
An secondary, often negative, effect that results from an action or policy.
副作用がある。
There is a side effect.
Examples
強い薬を飲んだため副作用で眠くなった。
I became sleepy due to a side effect of taking strong medicine.