What if I told you that there are no linguistic criteria to distinguish languages from dialects?
One person came up with the following answer:
“A language is a dialect with an army and navy” (Max Weinreich)
Max made the point that the definition is dependent on political realities that have nothing to do with linguistics.
The first part of finding a partial answer is mutual intelligibility:
When two languages are mutually intelligible, they are dialects. If they are not understood, they are languages.
This is a very slippery answer because it is difficult to pin down “mutually intelligible”.
A big problem with this approach is dialect continuum:
Language A and B are mutually intelligible. B and C are mutually intelligible. A and C are NOT mutually intelligible. This is supposed to be very common with the Bantu languages.
If you really want to drive yourself nuts, think about the following. Latin is the mother tongue for Romance Languages;
wikipedia’s list of Romance Languages
- Ibero-Romance: Portuguese and Galician, Mirandese and Asturian-Leonese, Spanish, Aragonese
- Occitano-Romance: Catalan, Occitan
- Gallo-Romance: Langues d’oïl (including French), Franco-Provençal
- Rhaeto-Romance: Romansh, Ladin, Friulian
- Gallo-Italic languages
- Italo-Romance: Corsican, Italian, Neapolitan, Sicilian
- Dalmatian (extinct)
- Romanian: Daco-Romanian, Istro-Romanian, Aromanian, and Megleno-Romanian.
At some point each would have been a dialect of Latin, later becoming a separate language. The next time someone mentions romance languages, ask them when each transitioned from a dialect to a separate language.