효험이 · 효험을
efficacy, (proven) effect
Example
할머니는 이 차가 감기에 효험이 있다고 하셨어요.
Grandma said this tea works well for colds.
Word parts
효 effect+험 proof
Literally 'proven effect'.
Good to know
효험 sounds a bit old-fashioned; it's typical for folk remedies and traditional medicine.
Related words