Viking explorers had begun to settle Iceland in the 9th century, carrying with them the Old Norse language. Over time, Old Norse developed into "Western" and "Eastern" variants. Western Norse covered Norway and overseas settlements in Iceland, Greenland, the Faroe Islands and the Shetland Islands, while Eastern Norse developed in Denmark and south-central Sweden. The language of Iceland and Norway was practically the same up until the 14th century, when they started to deviate from each other. The language phase traditionally dated to 1350–1525 is known as Middle Norwegian and is seen by many as a transitional period from Old Norwegian to Modern Norwegian. The reason for this is that although most languages are in a state of constant change, Norwegian phonology, morphology and syntax changed considerably during this time. The use of grammatical case, and a great portion of the conjugation of verbs was lost and replaced by a more fixed syntax, use of prepositions and a greater use of auxiliary based verb forms. During the late Old Norse period and this period there was also a considerable adoption of Middle Low German vocabulary. Similar development in grammar and phonology happened in Swedish and Danish, keeping the dialect continuum in continental Scandinavia intact, but with greater dialectal variation. This process did not, however, occur in the same way in Faroese and Icelandic. These languages remain conservative to this day, when it comes to grammar and vocabulary, so mutual intelligibility with continental Scandinavia was lost.