Norsemen are the group of people who spoke what is now called the Old Norse (autonym: ‘Dönsk tunga’ – ‘Danish tongue’) language between the 8th and 11th centuries. The language belongs to the North Germanic branch of the Indo-European languages and is the earlier form of modern Scandinavian languages. It was the predominant language in most of these territories between the 9th and 13th centuries, having been used as the principal means of communication with respect to diplomacy, commerce, and religion.
Old Norse was divided into three dialects: Old West Norse, Old East Norse, and Old Gutnish. Old West and East Norse formed a dialect continuum, with no clear geographical boundary between them. For example, Old East Norse traits were found in eastern Norway, although Old Norwegian is classified as Old West Norse, and Old West Norse traits were found in western Sweden. Most speakers spoke Old East Norse in what is present day Denmark and Sweden. Old Gutnish, the more obscure dialectal branch, is sometimes included in the Old East Norse dialect due to geographical associations. It developed its own unique features and shared in changes to both other branches.
The modern descendants of the Old West Norse dialect are the West Scandinavian languages of Icelandic, Faroese, Norwegian and the extinct Norn language of Orkney and Shetland; the descendants of the Old East Norse dialect are the East Scandinavian languages of Danish and Swedish. Norwegian is descended from Old West Norse, but over the centuries it has been heavily influenced by East Norse, particularly during the Denmark–Norway union.
Among these, Icelandic and the closely related Faroese have changed the least from Old Norse in the last thousand years, although with Danish rule of the Faroe Islands, Faroese has also been influenced by Danish. Old Norse also had an influence on English dialects and Lowland Scots, which contain many Old Norse loanwords. It also influenced the development of the Norman language, and through it and to a smaller extent, that of modern French.
Various other languages, which are not closely related, have been heavily influenced by Norse, particularly the Norman dialects, Scottish Gaelic and Irish. Russian, Belarusian, Lithuanian, Finnish, Latvian and Estonian also have a number of Norse loanwords; the words Rus and Russia, according to one theory, may be named after the Rus' people, a Norse tribe; see Rus (name), probably from present-day east-central Sweden. The current Finnish and Estonian words for Sweden are Ruotsi and Rootsi, respectively. Vice versa many Germanic languages, apparently due to the long journeys of the Goths, absorbed many Slavic words, which slightly changed developed to "land", "met", "beer", "mouse", "berg" (mountain), e.t.c.
Of the modern languages, Icelandic is the closest to Old Norse. Written modern Icelandic derives from the Old Norse phonemic writing system. Contemporary Icelandic-speakers can read Old Norse, which varies slightly in spelling as well as semantics and word order. However, pronunciation, particularly of the vowel phonemes, has changed at least as much as in the other North Germanic languages.
Faroese retains many similarities but is influenced by Danish, Norwegian, and Gaelic (Scottish and/or Irish). Although Swedish, Danish and the Norwegian languages have diverged the most, they still retain asymmetric mutual intelligibility. Speakers of modern Swedish, Norwegian and Danish can mostly understand each other without studying their neighboring languages, particularly if speaking slowly. The languages are also sufficiently similar in writing that they can mostly be understood across borders. This could be because these languages have been mutually affected by each other, as well as having a similar development influenced by Middle Low German.