偉い効こう

noun

great effect; remarkable efficacy

Rare literary noun; used in formal or classical contexts to describe a powerful or outstanding effect, often of medicine, treatment, or effort.

• この薬くすりは病やまいに偉い効こうを奏そうしたと古こ文ぶん書しょにある。

  Ancient documents say this medicine had a great effect on the illness.