A characteristic of objects that allows them to respond differently to the same message.

A central concept of object-oriented design. Polymorphism applies a class's interface to many different subclasses. Through polymorphism, you can send the same message to different objects of different types and have them respond appropriately for their type. An instance of the subclass can stand in for the superclass. The superclass code is unaware of the actual type of the object it has been passed.

The principle that allows an object of a specific type to also be treated as an instance of any of its supertypes.

The principle that allows a derived class to override the methods of its superclass with its own definitions.