(1) In key-value coding, a property that is a simple value, such as a scalar, string, or Boolean value, or to immutable objects such as NSColor and NSNumber objects. (2) In AppleScript, one of the two main descriptor data types that make up an Apple event. Not commonly used by scriptable Cocoa applications. (3) In an XML file, a name-value pair that specifies a single property for an element. (4) In Keychain Services, One data item, such as the name, type, date modified, account number, and so on, for a keychain item, other than the secret. The attributes associated with a keychain item depend on the class of the item. (5) In Entity-Relationship modeling, an identifiable characteristic of an entity. For example, lastName can be an attribute of an Employee entity. An attribute typically corresponds to a column in a database table.