In programming languages and type theory, polymorphism (from Greek , polys, "many, much" and , morphe, "form, shape") is the provision of a single interface to entities of different types. A polymorphic type is one whose operations can also be applied to values of some other type, or types. There are several fundamentally different kinds of polymorphism:

• Ad hoc polymorphism: when a function denotes different and potentially heterogeneous implementations depending on a limited range of individually specified types and combinations. Ad hoc polymorphism is supported in many languages using function overloading.
• Parametric polymorphism: when code is written without mention of any specific type and thus can be used transparently with any number of new types. In the object-oriented programming community, this is often known as generics or generic programming. In the functional programming community, this is often shortened to polymorphism.
• Subtyping (also called subtype polymorphism or inclusion polymorphism): when a name denotes instances of many different classes related by some common superclass. In the object-oriented programming community, this is often simply referred to as polymorphism.