Grimm's Law (First Consonant Shift)


First Stage .
/bh/ (voiced bilabial aspirate) became /b/ (voiced bilabial fricative)
/dh/ (voiced alveolar aspirate) became /ð/ (voiced interdental fricative)
/gh/ (voiced velar aspirate) became /g/ (voiced velar fricative)
.
Second Stage .
/p/ (voiceless bilabial stop) became /f/ (voiceless labio-dental fricative)
/t/ (voicless alveolar stop) became /q/ (voiceless interdental fricative)
/k/ (voicless velar stop) became /h/ (voiceless velar fricative)

Third Stage .
/b/ (voiced bilabial stop) became /p/ (voiceless bilabial stop)
/d/ (voiced alveolar stop) became /t/ (voiceless alveolar stop)
/g/ (voiced velar stop) became /k/ (voiceless velar stop)
.
Fourth Stage .
/b/ (voiced bilabial fricative) became /b/ (voiced bilabial stop)
/ð/ (voiced interdental fricative) became /d/ (voiced alveolar stop)
/g/ (voiced velar fricative) became /g/ (voiced velar stop)


Grimm's Law does not apply to *IE voiceless stops (that is, /p/, /t/, /k/) following another voiceless stop or /s/. See also Verner's Law.