• subclass

    A class that inherits variables and methods from an existing class.

  • superclass

    The class from which variables and methods are inherited.

  • Object

    The class that is the root of the tree-structured class hier- archy.

  • overriding

    Specifying a method in a subclass for the same message as a method in a superclass.

  • super

    A pseudo-variable that refers to the receiver of a message; differs from self in where to start the search for methods.

  • abstract class

    A class that specifies protocol, but is not able to fully im- plement it; by convention, instances are not created of this kind of class.

  • subclassResponsibility

    A message to report the error that a subclass should have implemented one of the superclass’s messages.

  • shouldNotImplement

    A message to report the error that this is a message inherited from a superclass but explicitly not available to instances of the subclass.