additive effect
Technical term used in pharmacology, statistics, and other scientific fields to describe a combined effect equal to the sum of individual effects.
An additive effect was observed between these two drugs.
Please explain the difference between additive effect and synergistic effect.
相乗効果 (synergistic effect) means the combined effect is greater than the sum of individual effects, while 相加効果 is simply the sum.
Compound of 相加 (sōka, 'addition, adding together') and 効果 (kōka, 'effect'). The term is a direct calque from English 'additive effect'.