A set of complex historical sound changes, first discovered by Friedrich von Schlegel and Rasmus Rask, but developed and publicised by Jakob Grimm of fairy tale fame. The changes relate the plosive system reconstructed for Proto-Indo-European (PIE) to that of Proto-Germanic (PGmc) and explain the differences between Germanic languages and other Indo-European languages, such as Greek and Latin, which were not subject to the changes. For example, compare Latin pater, piscis etc. to English father, fish etc.
The PIE plosive system is reconstructed as having:
- p t k which were replaced by f θ x in PGmc
- b d ɡ which were replaced by p t k in PGmc
- bʱ dʱ ɡʱ which were replaced by b d ɡ in PGmc
Apparent exceptions to Grimm’s law are dealt with by the later Verner’s law.
Also called Rask’s-Grimm’s Rule or The First Germanic Sound Shift.