The largest Vietnamese immigrant community in the United States located in Orange County, California. It is made up of an overwhelming number of shopping centers, supermarkets and restaurants and also contains the largest Vietnamese population outside of Viet Nam.

Literally everyone, ever. Including the writer of this definition.

Any neighborhood with a significant Vietnamese presence

e.g. the Southside neighborhood of Louisville KY & the Tenderloin District in San Francisco.

Many are a separate enclave within a larger, pre established Chinatown.