Since 1992 the „European Charter for Regional or Minority Languages” is being discussed in Europe together with opportunities and ways for the protection of lesser used languages, dialects are not rated among these. This points to linguistic difficulties on how to define regional and minority languages linguistically compatible. This will be discussed in the article with an emphasis on the particular difficulties of the regional languages. Ultimately everything amounts to a definitional practice in which it is essential not to intermingle language politics with linguistic science. This, however, has happened in the discussion about the charter in Germany (with regard to Low German) as well in the Netherlands (with regard to Low Saxon, Limburgish and Zeelandic). The discussions are indirectly a plea for linguistic science to contribute to debates on linguistic politics so that these do not lose their substantial core of matter.