When an "is a" relationship exists between objects, it means that the specialized object has all the characteristics of the general object plus additional characteristics that make it special.

This characteristics is called Polymorphism in the concept of Object Oriented Programming.

Explanation:

Polymorphism is one of the characteristics of Object Oriented Programming (OOP). It is also known as an "is a" relationship between objects.

Polymorphism is the ability of an object to take on many forms. It is commonly used when a parent class reference is used to refer to a child class object.

For instance; we have an Animal class, then a Dog class which inherit from the Animal class. We can then say a Dog is an animal (Polymorphism).