a feeling of loyalty or affiliation to a particular region, especially in political, cultural, or economic terms, or a theory in which a particular region governs itself instead of being centrally governed;
e.g. The country followed a policy of regionalism in which states formed their own governments.
(noun)
a characteristic feature of the language spoken in a region that is not standard to the language itself;
e.g. This figure of speech is a regionalism that is only used by people who are from this area.