Any thing that exist in more than one form is known as the polymorphism.
Example of ploymorphism. 1. Abstract class(Because, In the abstract super class its define some general information, In the subclass it must be override. It it's many form.(It supports single Inheritance))
2. Interface( same as above but supporting multiple inheritance )
3. Method overloading( In the class having a method is same return type but different signature )