Dialect levelling

Dialect levelling (or leveling in American English) is an overall reduction in the variation or diversity of a dialect's features when in contact with one or more other dialects. This can come about through assimilation, mixture, and merging of certain dialects, often amidst a process of language codification, which can be a precursor to standardization. One possible result is a koine language, in which various dialects mix together and simplify, settling into a new and more widely embraced form of the language. Another possible path is that a speech community increasingly adopts or exclusively preserves features with widespread social currency at the expense of their more local or traditional dialect features.

Dialect levelling 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 be observed in pre-industrial times too, 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.

Dialect levelling has been defined as the process by which structural variation in dialects is reduced, "the process of eliminating prominent stereotypical features of differences between dialects", "a social process [that] consists in negotiation between speakers of different dialects aimed at setting the properties of, for example, a lexical entry", "the reduction of variation between dialects of the same language in situations where speakers of these dialects are brought together", "the eradication of socially or locally marked variants (both within and between linguistic systems) in conditions of social or geographical mobility and resultant dialect contact", and the "reduction... of structural similarities between languages in contact", of which "interference and convergence are really two manifestations".

Leonard Bloomfield implicitly distinguished between the short-term process of accommodation between speakers and the long-term process of levelling between varieties and between the social and the geographical dimensions. On the geographical dimension, levelling may disrupt the regularity that is the result of the application of sound laws. It operates in waves but may leave behind relic forms. Dialect levelling and Mischung, or dialect mixing, have been suggested as the key mechanisms that destroy regularity and the alleged exceptionlessness of sound laws.

Dialect levelling is triggered by contact between dialects, often because of migration, and it has been observed in most languages with large numbers of speakers after the industrialisation and the modernisation of the area or areas in which they are spoken. It results in unique features of dialects being eliminated and "may occur over several generations until a stable compromise dialect develops". It is separate from the levelling of variation between dialectal or vernacular versions of a language and standard versions.

Contact leading to dialect levelling can stem from geographical and social mobility, which brings together speakers from different regions and social levels. Adolescents can drive levelling, as they adapt their speech under the influence of their peers, rather than their parents.^{[better source needed]}

In 20th-century British English, dialect levelling was caused by social upheaval leading to larger social networks. Agricultural advancements caused movement from rural to urban areas, and the construction of suburbs caused city-dwellers to return to former rural areas. The World Wars brought women into the workforce and men into contact with more diverse backgrounds.

While written and spoken language can diverge significantly, the presence of long distance communication – which prior to inventions such as the telephone was virtually always written – usually drives or necessitates the use of a lingua franca, dialect levelling or both. To be understood by their correspondence partners farther away, authors will naturally tend to reduce exceedingly local forms and incorporate loanwords from the dialect of the person they're writing to. If enough such correspondence is undertaken over a long enough time frame by enough people a new written standard or de facto standard can emerge. Examples include Middle Low German as employed by the Hanseatic League or Koine Greek. In the absence of long distance communication and travel, languages and dialects can diverge significantly in comparatively short time spans.