Dialect Continuum

A dialect continuum is a range of dialects spoken across a large geographical area, differing only slightly between areas that are geographically close to each other, and gradually decreasing in mutual intelligibility as the distances become greater. Dialects separated by great geographical distances may not be mutually comprehensible. According to the Ausbausprache - Abstandsprache - Dachsprache paradigm, these dialects can be considered Abstandsprachen (i.e., as stand-alone languages). However, they also can be seen as dialects of a single language, provided that a common standard language, through which communication is possible, exists.
Continental West Germanic

The many regional dialects of German are often cited as the canonical example of a dialect continuum. They form a single dialect continuum, with three recognized literary standards. Although Dutch and standard German are not mutually intelligible, there are transitional dialects that are, for example, Limburgish, spoken in parts of the Netherlands, Belgium and a very small part of Germany, and some other Low Franconian dialects spoken across the border in Germany which are known as South Guelderish (however, Limburgish is nowadays sometimes considered a language in its own right).

Another example was the area where the river Rhine crosses the border from Germany to the Netherlands. On both sides of this border, the people living in the immediate surroundings spoke an identical language. They could understand each other without difficulty, and would even have had trouble telling just by the language whether a person from the region was from the Netherlands or from Germany. However, the Germans here called their language German, and the Dutch called their language Dutch, so in terms of sociolinguistics they were speaking different languages.

Romance languages

The Italo-Western branch of the Romance languages, which comprises Italian, Spanish, French and Portuguese, as well as other languages