(1) In OSI, the representation of a layer on a given open system.
(2) A person, object, or concept about which information is stored.
(3) In markup languages such as XML, a collection of characters that can be referenced as a unit, for example to incorporate often-repeated text or special characters within a document.
(4) In object-oriented design, an item that can be treated as a unit and, often, as a member of a particular category or type. An entity can be a concrete thing or an abstract idea.
(5) A user, group, or resource that is defined to RACF.