The Japonic languages reference article from the English Wikipedia on 24-Apr-2004
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Japonic languages

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The Japonic family of languages are a group of languages related to Japanese, believed to descend from a common language known as Proto-Japonic. The Japonic languages have been postulated to belong to the Altaic languages, but there is no empirical proof of a relationship.

The Japonic languages are:

Whether the various Ryukyuan languages are separate languages or merely dialects is debatable.