Polymorphism

In the field of computer programming, polymorphism refers to the ability of a derived class to redefine, or override, methods that it inherits from a base class. You do this when you need to do something specific in a method that is either different or else not defined in the base class. For example, the Animal.MoveLeft method, since it must be very general in order to be valid for all animals, is probably very simple: something like "change orientation so that animal's head is now pointing in direction X". However, in your Cat class, this might not be sufficient. You might need to specify how the Cat moves its paws and tail while it turns. And if you have also defined a Fish class or a Bird class, you will probably need to override the MoveLeft method in different ways for each of those classes also. Because you can customize the behavior of the MoveLeft method for your particular class, the code that creates your class and calls its methods does not have a separate method for each animal in the world. As long as the object inherits from Amimal, the calling code can just call the MoveLeft method and the object's own version of the method will be invoked.