This is the 7995th most frequent Russian word.
кореей
"Корее́й" is the instrumental case of "Корея," meaning "Korea."
Used to indicate interest in a country, in this case, Korea.
Я интересуюсь культурой Кореи.
I am interested in Korean culture.
Used to denote traveling to a country, specifically Korea.
Он вернулся из поездки в Корею.
He returned from a trip to Korea.
Used in discussing the historical aspects of a country, Korea.