Entity

An entity is something that exists as a distinct being or thing. In philosophy, entities are the basic constituents of reality that can be identified, named, or described, including concrete objects and abstract notions such as numbers or properties. The term derives from the Latin entitas, from esse, to be.

In information science, the term is used to denote a thing with a unique identity and attributes. In database design and the entity-relationship model, an entity type represents a class of things; instances are the individual records. Entities have attributes (properties) and may participate in relationships with other entities. A primary key uniquely identifies each instance.

In natural language processing, named entities are real-world objects such as persons, organizations, locations, or dates that are mentioned in text. Entity recognition or extraction aims to identify these mentions and often links them to a knowledge base (entity linking). The concept extends to knowledge graphs where entities are nodes connected by relationships.

In law and business, an entity may refer to a unit with legal personality, such as a corporation, capable of owning assets and assuming obligations independently of its owners.

In mathematics and logic, the term is used to refer to objects that can be the subject of discussion within a formal framework, including numbers, sets, or functions, depending on the theory.