The most common Korean word for “mainly” is 주로 (juro). 「mainly」는 한국어로 주로.
Learn 주로 free — flashcards, audio and review →「주로」 단어장으로 무료로 외우기Words and levels: TOPIK I essentials (National Institute of Korean Language standard curriculum, KOGL Type 1) · examples: Cheesepotato