Verner's law, stated by
Karl Verner in 1875, describes a historical
sound change in the
Proto-Germanic language whereby voiceless
fricatives *
f, *
þ, *
s, *
h, *
hʷ, when immediately following an unstressed syllable in the same word, underwent voicing and became respectively the fricatives *
b, *
d, *
z, *
g, *
gʷ.