Verner’s law

Verner’s law is a follow-up to Grimm’s law, describing the consonantal changes that occurred as Proto-Germanic developed from Proto-Indo-European.

What Verner found is that a series of unvoiced consonants became voiced in Proto-Germanic if they were not at the start of a word, and if the vowel preceding them in PIE was unstressed.

1 2
ɸ β
θ ð
x ɣ
s z

In the table above, column 1 represents the phoneme as it was at the end of the change described by Grimm’s law. Column 2 represents the phoneme as it was after Verner’s law was executed as well.

After Verner’s law, Proto-Germanic underwent a change in stress, where it shifted to the first syllable; this obscured the context in which Verner’s law occurred at first, but because the original PIE stress was preserved in Greek and early Sanskrit, it could be reconstructed.

There is some debate about whether the Verner’s law sound change actually occurred after the Grimm’s law sound change. It’s easier to explain if you assume it occurred afterwards, but it could have occurred before and then Grimm’s law would just be more complicated, with phonemes’ positions within words becoming relevant. Some linguists argue that the Verner’s law change did come first, and apparently this position is becoming more common over time, but I’m not sure the evidence for this (perhaps it’s difficult to explain to laypeople).