Entities

An entity is something that exists as a distinct, identifiable unit. In philosophy and ontology, an entity is any being with its own identity, whether concrete or abstract. In information science, an entity often denotes a discrete item stored in a data system, capable of being uniquely identified and described by attributes.

Entities are typically categorized as concrete or abstract. Concrete entities include physical objects like a chair or a person; abstract entities include numbers, concepts, or ideas. In linguistics, entities are the referents of noun phrases, the things that language talks about, which may be real or fictional.

In databases and knowledge representations, an entity type describes a class of objects, while an entity instance is a single realized object, such as a particular customer or location. Attributes describe properties of the entity, and relationships link entities to other entities. Entity resolution or deduplication seeks to determine when multiple data records refer to the same real-world entity. In linked data, entities are identified by unique identifiers such as URIs.

The term is also used in law and business to describe a person or organization regarded as having legal rights and duties, such as a corporation or government agency. Across disciplines, entities provide a practical unit for modeling, analysis, and communication, allowing complex systems to be described in terms of their constituent parts and their interrelations.