There are degrees of communication though, and degrees of distance between languages. For example, Scandinavians can typically make themselves understood with s

There are degrees of communication though, and degrees of distance between languages. For example, Scandinavians can typically make themselves understood with speakers of other Scandinavian languages, but they're not the same language. Same with Spanish and Italian. I'd have have to expend similar effort with someone speaking Jamaican Patois or thick Glaswegian English. I guess my point is that it's a simple task to label languages if you apply prior knowledge of their historical context, but it might not be the most useful categorisation, either in terms of linguistic similarity or in terms of regional identity of the speaker