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Language

The 12th-century Icelandic Gray Goose Laws (Icelandic: grágás) state that Swedes, Norwegians, Icelanders, and Danes spoke the same language, dǫnsk tunga ("Danish tongue"; speakers of Old East Norse would have said dansk tunga). Another term was norrœnt mál ("northern speech"). Old Norse has developed into the modern North Germanic languages: Icelandic, Faroese, Norwegian, Danish, Swedish, and other North Germanic varieties of which Norwegian, Danish and Swedish retain considerable mutual intelligibility while Icelandic remains the closest to Old Norse. In present-day Iceland schoolchildren are able to read the 12th-century Icelandic sagas in the original language (in editions with normalised spelling).

Written sources of Old Norse from the Viking Age are rare: there are rune stones, but the inscriptions are mostly short. A good deal of the vocabulary, morphology, and phonology of the runic inscriptions (little is known definitely about their syntax) "can be shown to develop regularly into Viking-Age, medieval and modern Scandinavian reflexes ", says Michael Barnes.

According to David Arter, Old Norse was for a while during the Viking Age a lingua franca spoken not just in Scandinavia but also in the courts of the Scandinavian rulers in Ireland, Scotland, England, France and Russia. The Norse origin of some words used today is obvious, as in the word haar referring to the cold sea mist on the east coast of Scotland and England; it derives from the Old Norse haárr.