Benrath line

The benrath line is a line on a map that separates different dialects of German. Imagine if you and your friend both spoke German but had slightly different ways of saying things. Maybe one of you says "papa" for dad and the other says "vati". The benrath line is like a border that separates areas where people say "papa" from those where people say "vati" and other variations. It's named after a city called Benrath where linguists first studied this variation in the 19th century.