Evolutionary phonology

 Evolutionary Phonology is an approach to phonology and historical linguistics, based on the idea that recurrent synchronic sound patterns, if not inherited from the mother tongue, are the result of recurrent sound changes, while rare patterns are the product of rare changes or a combination of independent changes.[1]

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
Attribution-ShareAlike 3.0 Unported License
.