Chapter 4 demonstrates that Korean has deeply influenced its immediate language neighbors: Japanese and Jurchen-Manchu. The Japanese-Korean parallels discussed here have often been presented as proof of their genetic relationship. However, the chapter argues that the overwhelming majority of these parallels are found only in Central Japanese, the Japonic language, with which Korean was in immediate and direct contact. On the other hand, most of the Korean-Jurchen/Manchu comparisons dealt with in this chapter have not previously been discussed. With few exceptions, they are found only in Jurchen and Manchu but not in other Tungusic languages. These exceptions are easily explained as loans from Jurchen or Manchu into the neighboring Southern or Northern Tungusic languages; they are never found in those Northern Tungusic languages, such as Ewenki and Ewen that are located outside of the area.

Chapter 2 outlines the history of the Korean language, starting from the internal reconstruction of proto-Korean through Old Korean, Middle Korean, Modern Korean and Contemporary Korean. Old Korean designates the language of Silla up until the end of the Unified Silla period in the tenth century. Middle Korean covers the Koryo (Early Middle Korean) and Choson (Late Middle Korean) periods up until the end of the sixteenth century. This relatively brief period has also seen events of great linguistic importance: the Japanese colonial period (1909 to 1945), which saw the importation of Japanese loans and loans from Western languages through Japanese; the Korean War, resulting in the division of the two Koreas; and finally the turbulent postwar period, which has seen the final disappearance of Chinese characters in the Democratic People’s Republic of Korea and the near complete disappearance of them in the Republic of Korea, and the ever greater impact of neologisms and loans from electronic media and the internet.