The most common Korean word for “no” is 아니요 (aniyo). There is one more word with a similar meaning — compare them below. 「no」는 한국어로 아니요.
no; no sir; no ma'am
TOPIK 1 · interjection
Words and levels: TOPIK I essentials (National Institute of Korean Language standard curriculum, KOGL Type 1) · examples: Cheesepotato