Hanja were first introduced into the Korean Peninsula during the Chinese Han (한; 漢) Dynasty (202 BC - AD 220) - largely through the Cheonjamun (천자문; 千字文; Thousand-Character Classic) - and their introduction into Korea was closely tied to the spread of Buddhism.
Although many of the most frequently used words in Korean are of native Korean origin, Sino-Korean words today make up over 70% of the Korean vocabulary.