The act of providing a single interface to entities of different data types (objects for example). A polymorphic type is a data type whose operations can also be applied to values of some other type.
Where polymorphic functions can be applied to arguments of different types (often through function overloading). + can be used like 1 + 3.7 = 4.7 or int + float = float. It also overloaded in some languages to do "bab" + "oon" = "baboon".
Non type specific code, called generics.
When a name denotes instances of many different subclasses of a superclass (polymorphism in OOP).
A feature of The process of selecting which implementation of a polymorphic operation to call at run time. A prime characteristic of object oriented programming languages. It is desirable to name multiple methods with the same name, whose functionality is similar, but operate on multiple types.
Static dispatch, the implementation of a polymorphic operation is selected at compile-time. Dynamic dispatch provides support for cases where the appropriate implementation cannot be determined at compile time, because it depends on the runtime type.
The decision of which version of a method to called can be based on a single object or many objects. Single dispatch is supported by OOP languages like smalltalk, C++, ruby, where the object itself. Multiple dispatch is a generalized form of single dispatch, where functions are dispatched based on multiple objects.