(1) In Java, a group of methods that can be implemented by several classes, regardless of where the classes are in the class hierarchy.
(2) In object-oriented programming, an abstract model of behavior; a collection of functions or methods.
(3) A shared boundary between independent systems. An interface can be a hardware component used to link two devices, a convention that supports communication between software systems, or a method for a user to communicate with the operating system, such as a keyboard.
(4) A collection of operations that are used to specify a service of a class or a component. See also class, port type.
(5) In UML modeling, a model element that defines sets of operations that other model elements, such as classes or components, must implement.