Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed common ancestor of the Germanic languages.
A defining feature of Proto-Germanic is the completion of the process described by Grimm's law, a set of sound changes that occurred between its status as a dialect of Proto-Indo-European and its gradual divergence into a separate language. The end of the Common Germanic period is reached with the beginning of the Migration Period in the fourth century AD.