Polymorphism — polymorphism is behavior that varies depending on the class in which the behavior is invoked, that is, two or more classes can react differently to the same message. 

Polymorphism means allowing a single definition to be used with different types of data (specifically, different classes of objects). For instance, a polymorphic function definition can replace several type-specific ones, and a single polymorphic operator can act in expressions of various types. Many programming languages and paradigms implement some forms of polymorphism.

The concept of polymorphism applies to data types in addition to functions. A function that can evaluate to and be applied to values of different types is known as a polymorphic function. A data type that contains elements of different types is known as a polymorphic data type.

See details at wikipedia.org.