The core of the Korean vocabulary is made up of native Korean words. More than 50% of the vocabulary (up to 70% by some estimates), however, especially scholarly terminology, are Sino-Korean words[citation needed], either directly borrowed from Written Chinese, or coined in Japan or Korea using Chinese characters.

Korean has two number systems: one native, and one borrowed from the Chinese.

To a much lesser extent, words have also occasionally been borrowed from Mongolian, Sanskrit, and other languages. Conversely, the Korean language itself has also contributed some loanwords to other languages, most notably the Tsushima dialect of Japanese.

In modern times, many words have been borrowed from Japanese and Western languages such as German (areubaiteu ‘part-time job’, allereugi ‘allergy’) and more recently English. Concerning daily usage vocabulary except what can be written in hanja, more words have possibly been borrowed from English than from any other language. Some Western words were borrowed indirectly via Japanese, taking a Japanese sound pattern, for example ‘dozen’ > ダース dāsu > 다스 daseu.

Most indirect Western borrowings are now written according to current hangulization rules for the respective Western language, as if borrowed directly. There are a few more complicated borrowings such as ‘German(y)’ (see Names for Germany), the first part of whose endonym [ˈd̥ɔɪ̯ʧʷ.la̠ntʰ] the Japanese approximated using the kanji 獨逸 doitsu that were then accepted into the Korean language by their Sino-Korean pronunciation: 獨 dok + 逸 il = Dogil.

In South Korean official use, a number of other Sino-Korean country names have been replaced with phonetically oriented hangulizations of the countries’ endonyms or English names.

North Korean vocabulary shows a tendency to prefer native Korean over Sino-Korean or foreign borrowings, especially with recent political objectives aimed at eliminating foreign (mostly Chinese) influences on the Korean language in the North. By contrast, South Korean may have several Sino-Korean or foreign borrowings which tend to be absent in North Korean.