Polymorphism
Polymorphism is the presentation of one interface for multiple data types.
For example, integers, floats, and doubles are implicitly polymorphic: regardless of their different types, they can all be added, subtracted, multiplied, and so on.
In the case of OOP, by making the class responsible for its code as well as its own data, polymorphism can be achieved in that each class has its own function that (once called) behaves properly for any object.
See also
- Polymorphism on Wikipedia