Translation guide
A secondary or incidental result of a process, often unintended but sometimes useful. In Japanese, different words emphasize whether the result is natural, unwanted, or a side effect.
A substance produced during the manufacture of something else, often useful.
The most common and neutral term for a by-product, especially in industrial or economic contexts. Can also be used metaphorically.
At this factory, fertilizer is produced as a by-product.
Similar to 副産物 but often used in biological or chemical contexts for a secondary product.
Alcohol is produced as a by-product of fermentation.
An incidental result of an action or event, often negative or neutral.
Primarily means 'side effect' (especially of medicine), but can be used more broadly for unintended negative consequences.
Drowsiness is a side effect of this medicine.
A more formal term for a secondary effect, often used in analysis or reports. Can be positive or negative.
Literally 'afterwaves', used for ripple effects or aftermath, often negative. More literary.
A beneficial result that was not the main goal.
Literally 'unexpected by-product', used for a pleasant surprise or unintended benefit.
An unexpected by-product of this project was that the team's unity strengthened.
Casual term for a bonus or extra, often used for a small added benefit. Not formal.
副産物 is neutral and often implies a tangible secondary product, while 副作用 is specifically a side effect, usually negative or medical. Use 副産物 for industrial or metaphorical by-products, and 副作用 for unintended consequences, especially harmful ones.
The English 'by-product' is often used metaphorically for any incidental result. In Japanese, 副産物 can be used metaphorically, but 副作用 or 副次的効果 may be more natural depending on context. Avoid directly translating 'by-product' as バイプロダクト, which is not standard Japanese.
経済成長の副作用として環境汚染が進んだ。
Environmental pollution progressed as a side effect of economic growth.
As a secondary effect of that policy, the local economy was revitalized.
Many people suffered in the aftermath of the war.
The fun of this job is like a bonus.