Translation guide
The ability to produce a desired result, especially in medicine, treatment, or measures. In Japanese, the most common equivalent is 有効性 (yūkōsei), but other terms like 効能 (kōnō) or 効き目 (kikime) are used depending on context.
Referring to the power or capacity to produce an effect, often in scientific, medical, or policy contexts.
The standard term for 'efficacy' in formal contexts, especially in medicine, science, and policy. It emphasizes proven effectiveness under ideal conditions.
この薬の有効性は臨床試験で確認された。
The efficacy of this drug was confirmed in clinical trials.
Often used for the beneficial effects of medicines, treatments, or health products. Slightly more consumer-oriented than 有効性.
このサプリメントの効能には疲労回復が含まれる。
The efficacy of this supplement includes recovery from fatigue.
A broader term for 'effect' or 'effectiveness'. Can be used for efficacy in everyday contexts, but less precise than 有効性.
新しい政策の効果を評価する必要がある。
We need to evaluate the efficacy of the new policy.
Describing how well something works in real-life situations, often for remedies, methods, or personal experiences.
Commonly used for the tangible effect of medicine, treatments, or measures. Conveys a sense of 'it works' in a practical sense.
この痛み止めはすぐに効き目が現れた。
This painkiller showed its efficacy right away.
Verb meaning 'to be effective'. Used in casual conversation to say something works.
この薬はよく効く。
This medicine has good efficacy.
Belief in one's own ability to succeed in specific situations, a term from psychology.
The standard translation for 'self-efficacy' in psychology. Refers to an individual's belief in their capacity to execute behaviors necessary to produce specific performance attainments.
自己効力感が高い人は困難な課題にも挑戦する。
People with high self-efficacy take on challenging tasks.
有効性 (yūkōsei) specifically means 'efficacy' under ideal or controlled conditions, often used in research. 効果 (kōka) is a broader term for 'effect' or 'effectiveness' in general, including real-world settings. Use 有効性 when precision is needed, such as in clinical trials.
ワクチンの有効性は95%だった。
The vaccine's efficacy was 95%.
ワクチンの効果は実際の使用で確認された。
The vaccine's effectiveness was confirmed in real-world use.
While 効力 (kōryoku) can mean 'effect' or 'validity', it is more commonly used for legal validity (e.g., of a contract) or potency. Using it for medical efficacy may sound unnatural. Stick to 有効性 or 効能.
この治療法の有効性は証明されている。
The efficacy of this treatment has been proven.
そのやり方の効果には疑問がある。
I doubt the efficacy of that approach.