Like Korean, Basque is a language isolate. While it has borrowed vocabulary from the romance languages, the way it’s written and spoken is distinct from any other language. This even extends to differences between the several versions of Basque that still exist. Despite being spoken by less than 700,000 people, there are at least five distinct Basque dialects, so not only is it tough to learn, but you need to pay attention to which version you’d like to learn as well.