Voiceless StopsVoiced StopsVoiced Aspirated Stops
Bilabial p -> f
ped(Lat) -> fot(OE)
b -> p
labium(Lat) -> lippa(OE)
bh -> b
bhrater(Skr) -> broþor(OE)
Alveolar t -> Θ
tres(Lat) -> þreo(OE)
d -> t
deka(Gk) -> ten(ModE)
dh -> d
medhios(OLat) -> mid(OE)
Velar k -> x/h
lux(Lat) -> leoht(OE)
g -> k
granum(Lat) -> corn(ModE)
gh -> g
ghomon(PIE) -> guma(OE)

Grimm’s Law (or the First Germanic Sound Shift) is a set of phonological changes that affects Proto-Indo-European (PIE) stops. The sound change, which likely occurred between 1000 BC and 1 BC, affected the Proto-Germanic branch of PIE and can be found in all of the Germanic languages. It accounts for some of the distinctive fricatives in English, and it helps prove the theory of language families through the comparison of cognates (or shared lexical items that differ through the predictable sound changes of Grimm’s law).