Historical Linguistics and Language Families 2, Exercise 3: rules and exceptions

Rule: b > v / V __ V   (Italian: b becomes v between vowels, as in
caballum > cavallo). This is a conditioned change, because it applies only
between vowels.

Verner and the Neogrammarians: Grimm noticed exceptions to his law. Verner
did not call them random; he explained them with a further law (voicing of
certain Germanic voiceless fricatives under specific conditions). That is the
Neogrammarian attitude: an apparent exception to a sound law has a cause, and
the work is to find it. The source lists analogy and dialect borrowing as other
causes of apparent exceptions. Lexical diffusion is the main challenge to the
claim that sound change is exceptionless.