Sino-Xenic or Sinoxenic pronunciations are regular systems for reading Chinese in Japan, Korea and Vietnam, originating in medieval times and the source of large-scale borrowings of Chinese words into the Japanese, Korean and Vietnamese languages, none of which are genetically related to Chinese. The resulting Sino-Japanese, Sino-Korean and Sino-Vietnamese vocabularies now make up a large part of the lexicons of these languages. The pronunciation systems are used alongside modern varieties of Chinese in historical Chinese phonology, particularly the reconstruction of the sounds of Middle Chinese. Some other languages, such as Hmong–Mien and Tai-Kadai languages, also contain large numbers of Chinese loanwords but without the systematic correspondences that characterize Sino-Xenic vocabularies.
The term, from the Greek xenos "foreign", was coined in 1953 by the linguist Samuel Martin, who called these borrowings "Sino-Xenic dialects".
There had been borrowings of Chinese vocabulary into Vietnamese and Korean from the Han period, but around the time of the Tang dynasty (618–907) Chinese writing, language and culture were imported wholesale into Vietnam, Korea and Japan. Scholars in those countries wrote in Literary Chinese and were thoroughly familiar with the Chinese classics, which they read aloud in systematic local approximations of Middle Chinese. With those pronunciations, Chinese words entered Vietnamese, Korean and Japanese in huge numbers.