In political geography, an enclave is a territory whose geographical boundaries lie entirely within the boundaries of another territory.
The word came late into the jargon of diplomacy in the English, coming from the French with a sense inherited from late Latin inclavatus meaning 'shut in, locked up"
Ethnic enclaves are communities of an ethnic group inside an area where another ethnic group predominates. Jewish ghetti and shtetlekh, barrios and Chinatowns are examples. These areas may have a separate language, culture and economic system.
From Websters: a distinct territorial, cultural, or social unit enclosed within or as if within foreign territory