Sprachbund

A Sprachbund (German for language union) is a group of languages that have become similar in some way because of geographical proximity. They may be genetically unrelated or only distantly related, but where genetic affiliations are unclear the Sprachbund characteristics might give a false appearance of relatedness.

One good instance is the way many languages of South-East Asia, including Thai and Vietnamese, have taken on the appearance of neighbouring languages like Chinese, with monosyllabic words and distinctive tones. Yet Thai and Vietnamese are no longer believed to be related to the Sino-Tibetan family.

In Europe, Albanian, Romanian, and Bulgarian are all Indo-European but from very different branches. Yet they share the grammatical feature of a postposed definite article. This does not occur in languages closely related to Romanian or to Bulgarian.

Many linguists think the Mongolian, Turkic, and Manchu-Tungus families of northern Asia are genetically related, in a group they call Altaic, but the evidence is equivocal, and their common features such as vowel harmony might instead mean they are part of a Sprachbund.