Benrath line
In German linguistics, the Benrath line (German: Benrather Linie) is the maken-machen isogloss: dialects north of the line have the original /k/ in maken (to make), while those to the south have /x/ (machen). The Line runs from Benrath (part of Düsseldorf) and Aachen to eastern Germany near Frankfurt an der Oder in the area of Berlin and Dessau.
The High German consonant shift (3rd to 9th centuries AD), in which the (northern) Low German dialects for the most part did not participate, affected the southern varieties of the West Germanic dialect continuum. This shift is traditionally seen to distinguish the High German varieties from the other West Germanic languages.
The impact of the High German consonant shift increases gradually to the South. The Benrath line does not mark the northernmost effect of the High German consonant shift, since the Uerdingen line, the ik-ich isogloss, lies slightly further north; and some of the peripheral changes associated with the shift did affect Low German.