"There is not universal agreement on the region’s components." [1]
"It can be difficult to define exactly which countries are included in the Balkan States. It is a name that has both geographic and political definitions, with some of the countries crossing what scholars consider the 'boundaries' of the Balkans." [2]
Almost the entire wikipedia article is dedicated to explaining the various definitions of it and how it is a problematic term. [3]
[1] https://www.britannica.com/place/Balkans
[2] https://www.thoughtco.com/where-are-the-balkan-states-407024...