Locality

Locality refers to the quality or state of being local, or to a location, place, or region that is close to a given point of reference. In everyday use, something local is associated with a particular place and its surrounding area, as opposed to the distant or global.

In geography and urban planning, locality is a defined area within a larger territory. Localities can be neighborhoods, districts, or census subdivisions, and they are used for governance, service delivery, and statistical reporting. The exact boundaries of a locality may be official, as in administrative units defined by government, or informal, reflecting common local understanding.

In physics, locality is a principle stating that an object is influenced directly only by its immediate surroundings, with causal interactions propagating at or below the speed of light. Locality underpins classical field theories and relativistic quantum field theory. Quantum mechanics introduces nonlocal correlations through entanglement, but these do not enable faster-than-light signaling and preserve overall locality in relativistic theories.

Variations of locality appear across disciplines. In linguistics and philosophy, locality concerns how knowledge or reasoning is anchored to nearby contexts. In criminology or public administration, locality helps organize data and services by geographic units.