Sound change typology

Definition
Sound changes can be classified and grouped together according to the type of change, its conditioning and other factors.

For a certain type of change, we can observe in which languages it occurred, and collections of attested sound changes then may show how frequent this type of change is. Some changes are very common, as, e.g., intervocalic voicing of voiceless stops:

[-son][-cont][-voiced] > [-son][-cont][+voiced] /[+voc]__[+voc] or (simplified and more concrete) p, t, k > b, d, g /V__V

It occurred, e.g., in the history of most Iranian languages, Middle Indo-Aryan, in Western Romance, British Celtic, Old Danish, in many Uralic languages etc.