It is set apart from neighboring dialect groups by characteristic features in the historical development of West Germanic vowels.
Unlike in earlier classifications, Wiesinger places the divide between Bergish (and South Low Franconian in general) and Kleverlandish/Westphalian not at the Uerdingen line, but further north.
Western Central Bergish is characterized by the merger of the MHG series ê – ô – ö̂ and ie – uo – üe to [iə] – [uə] – [üə] (still distinct in Eastern Central Bergish and the various Randbergisch varieties), and the retention of distinct verbal plural endings.
Eastern Central Bergish shares with the Randbergisch groups Mülheim, Werden, Barmen/Elberfeld, and Remscheid the generalized plural ending -en, probably influenced by Westphalian, which has the general plural ending -t. The Randbergisch groups of Mülheim, Werden, and Barmen/Elberfeld are located to the northeast of the Uerdinger line.
[6] He held the following views: Mengel (1967) distinguished in a broader sense of Bergish:[7] In a classification by Georg Cornelissen [de] based on isoglosses, dialects of the Bergisches Land are assigned to three dialect areas: varieties between the Uerdingen line (northern ik vs. southern ich 'I') and the Benrath line (northern maken vs. southern machen 'make') are grouped as South Low Franconian (e.g. around Remscheid), varieties south of the Benrath line are classified as Ripuarian (e.g. Bergisch Gladbach), while Ostbergisch ("East Bergish") designates a group of dialects in a long narrow stretch from Mülheim to Bergneustadt between the Uerdingen line (including its southeastern extension where it merges with the Benrath line east of Wermelskirchen) and the so-called Einheitsplurallinie (defined as the southwestern-most extension of the Westphalian generalized plural verb suffix -t).