by-product
nounUK /ˈbaɪˌprɒdʌkt/
US /ˈbaɪˌprɑːdʌkt/
A by-product is something extra that is made while you are making something else.
Sawdust is a by-product of cutting wood.
OTHER MEANINGS
2. A secondary result that happens because of something else.
Traffic jams are a by-product of too many cars in the city.
3. A substance left over from a manufacturing process.
The factory sells the ash from its furnaces as a by-product for making bricks.
4. An unexpected extra benefit or problem that comes with a main action.
Fame was an unwanted by-product of her viral video.