Sprachbund (en)

A Sprachbund is a linguistic area, i.e. set of geographically contiguous languages that are more similar to each other in their structure than would be expected on the basis on their degree of genealogical relatedness.

Term properties
Sometimes the German plural Sprachbünde is also used in English, and sometimes the term is italicized in English, as a non-assimilated loan. The term is usually capitalized.

Synonym

 * linguistic area

Origin
The term Sprachbund was coined by Nicholas Trubetzkoy in a contribution to the 1928 International Congress of Linguists (Trubetzkoy 1930). Apparently it occurred earlier in Trubetzkoy (1923), in the Russian form jazykovoj sojuz (cf. Reiter 1991:52), but it became widely known only after 1928.

Other languages
German Sprachbund