Dialect levelling

Dialect levelling or leveling (in American English) is the process of an overall reduction in the variation or diversity of features in a dialect due to contact with one or more other dialects. Typically, this comes about through assimilation, mixture, and merging of certain dialects, often by language codification: a precursor to standardization. One possible result is a koine language. It has been observed in most languages with large numbers of speakers after industrialization and modernization of the areas in which they are spoken. However, while less common, it could still be observed in pre-industrial times, especially in colonial dialects like American and Australian English or when sustained linguistic contact between different dialects over a large geographical area continues for long enough as in the Hellenistic world that produced Koine Greek as a result of dialect leveling from Ancient Greek dialects.