FWIW, https://en.wikipedia.org/wiki/Scandinavia points out:

> In English usage, Scandinavia also sometimes refers to the Scandinavian Peninsula, or to the broader region including Finland and Iceland, which is always known locally as the Nordic countries.

See also:

https://www.dictionary.com/browse/scandinavia?s=t "and sometimes Finland, Island, and the Faeroe Islands".

https://www.merriam-webster.com/dictionary/Scandinavia "Note: Some people also consider Iceland, the Faeroe Islands, and Finland to be part of Scandinavia"

https://www.goodreads.com/book/show/1187923.History_Of_Scand... - "History Of Scandinavia: Norway, Sweden, Denmark, Finland, And Iceland"

https://www.worldcat.org/title/live-work-in-scandinavia-denm... - "Live & work in Scandinavia : Denmark, Finland, Iceland, Norway, Sweden"

https://shop.lonelyplanet.com/products/discover-scandinavia-... - "Discover Scandinavia" travel guide "Coverage Includes: Reykjavik, Southeastern Iceland, the Blue Lagoon and the Golden Circle, Oslo, Norway’s Fjords, Stockholm, Gothenburg, Copenhagen, Tallinn, Estonia, Helsinki, Lakeland (Finland), the Far North and the Arctic Circle, and more"

To me (born and raised in Spain) "Scandinavia" and "The Scandinavian Peninsula" have always been synonyms. I was not aware the term had different acceptions.

To me, until now, Denmark was not in Scandinavia.

As another example of the cultural difference in what seems like a standard definition - English cultures generally says there are 7 continents, while Spanish cultures generally says there are 6, and that North and South America are two subcontinents. https://en.wikipedia.org/wiki/Continent#Number