They blend into each other. https://en.wikipedia.org/wiki/Rhenish_fan https://en.wikipedia.org/wiki/Rhenish_fan -- https://duckduckgo.com/?q=german+dutch+isoglo

They blend into each other. https://en.wikipedia.org/wiki/Rhenish_fan https://en.wikipedia.org/wiki/Rhenish_fan -- https://duckduckgo.com/?q=german+dutch+isoglosses&iar=images https://duckduckgo.com/?q=german+dutch+isoglosses&iar=images