Among the Indo-European languages, Dutch is grouped within the Germanic languages, meaning it shares a common ancestor with languages such as English, German, and the Scandinavian languages. All Germanic languages are subject to the Grimm’s law and Verner’s law sound shifts, which originated in the Proto-Germanic language and define the basic features differentiating them from other Indo-European languages. This is assumed to have taken place in approximately the mid-first millennium BCE in the pre-Roman Northern European Iron Age.
The Germanic languages are traditionally divided into three groups: East (now extinct), West, and North Germanic. They remained mutually intelligible throughout the Migration Period. Dutch is part of the West Germanic group, which also includes English, Scots, Frisian, Low German (Old Saxon) and High German. It is characterized by a number of phonological and morphological innovations not found in North or East Germanic. The West Germanic varieties of the time are generally split into three dialect groups: Ingvaeonic (North Sea Germanic), Istvaeonic (Weser-Rhine Germanic) and Irminonic (Elbe Germanic). It appears that the Frankish tribes fit primarily into the Istvaeonic dialect group with certain Ingvaeonic influences towards the northwest, which are still seen in modern Dutch.