The most common Korean word for “one” is 한 (han). There is one more word with a similar meaning — compare them below. 「one」는 한국어로 한.
one; a (before a counter)
TOPIK 1 · determiner
one
TOPIK 1 · noun
Words and levels: TOPIK I essentials (National Institute of Korean Language standard curriculum, KOGL Type 1) · examples: Cheesepotato