A set of classes and their interrelationships.One class may be a specialisation (a "subclass" or "{derived class}") of another which is one of its "{superclasses}" or "base classes".When a method is invoked on an object it is first looked for in the object' s class, then the superclass of that class, and so on up the hierarchy until it is found.Thus a class need only define those methods which are specific to it, and inherits methods from all its superclasses.See also: multiple inheritance.(1997-08-06)