Scandinavia
Norway, Sweden, Denmark, Iceland
Scandinavia includes Denmark, Norway, and Sweden. These countries have dominated Northern Europe throughout history, and have conquered Iceland and Finland in addition to other lands. They've spread their Scandinavian culture, languages, etc. to these lands, which is why Finland and Iceland are sometimes included in Scandinavia, but rarely. The term 'Nordic' refers to all five of these countries. Northern Europe most commonly includes these five countries.
Because of the Vikings, who attacked other countries.
Northern Europe is usually composed of only the Nordic countries: Denmark, Finland, Iceland, Norway, and Sweden. Scandinavia includes Denmark, Norway, and Sweden. These countries have dominated Northern Europe throughout history, and have conquered Iceland and Finland in addition to other lands. They've spread their Scandinavian culture, languages, etc. to these lands, which is why Finland and Iceland are sometimes included in Scandinavia, but rarely. The term 'Nordic' refers to all five of these countries.
Scandinavia is a region, not a country. It has no "official" language. The Scandinavian countries, with their official or national languages are: Denmark = Danish Norway = Norwegian Sweden = Swedish (Norwegian and Danish are dialects of each other, and Swedish is also very closely related).
The genes present on same chromosomes are sometimes linked to each other that inherit collectively are linked genes and can be separated by crossing over
The countries which make up the region of Scandinavia include Sweden, Denmark, Norway, Finland, and Iceland. However, the definition of Scandinavia varies a lot. Some would not include Iceland because it is nowhere near the Scandinavian peninsula and/or Finland because they don't speak a Scandinavian language.
Canada and the United States
In Finland (and some other countries like Russia) they claim that Santa Claus lives in Lapland, which is the Northern part of the Scandinavian peninsula. In reality Santa is of course living on Greenland, i.e. not in the geographical Scandinavia.
Iceland was ruled by Scandinavian countries for centuries. This caused Icelandic culture to be based on Scandinavian culture, the Icelandic language to be based off other Scandinavian languages, and the majority of Icelandics to be of Scandinavian descent. So in a way, Iceland could be considered a child of Scandinavia, as Scandinavia helped produce Iceland.
Scandinavian Airlines fly to a number of different countries. The airline flies out of Scandinavia, other parts of Europe, Canada, and the United States.