Although a mixture of different Asian peoples had migrated to the Korean Peninsula in past centuries, very few have remained permanently, so by 1990 both South Korea and North Korea were among the world's most ethnically homogeneous nations. The number of indigenous minorities was negligible. In South Korea, people of foreign origin, including Westerners, Chinese, and Japanese, were a small %age of the population whose residence was generally temporary. Like their Japanese neighbors, Koreans tend to equate nationality or citizenship with membership in a single, homogeneous ethnic group or "race" -minjok, in Korean. A common language and culture also are viewed as valuable elements in Korean identity. The idea of multiracial or multiethnic nations, like India or the United States, strikes many Koreans as odd or even contradictory. Consciousness of homogeneity is a major reason why Koreans on both sides of the DMZ viewed their nation's division as an unnatural and unnecessary tragedy.

All Koreans speak the Korean language, which is often classified as one of the Altaic languages, has affinities to Japanese, and contains many Chinese loanwords. The Korean script, known in South Korea as Hangul and in North Korea as Choson muntcha, is composed of phonetic symbols for the 10 vowels and 14 consonants. Korean often is written as a combination of Chinese ideograms and Hangul in South Korea, although the trend there is toward using less Chinese. A number of English words and phrases have crept into the language as a result of the American presence in the nation since 1950.