polymorphism

In computer science, polymorphism is a programming language feature that allows values of different data types to be handled using a uniform interface. The concept of parametric polymorphism applies to both data types and functions. A function that can evaluate to or be applied to values of different types is known as a polymorphic function. A data type that can appear to be of a generalized type (e.g., a list with elements of arbitrary type) is designated polymorphic data type like the generalized type from which such specializations are made.

Example:

program Adhoc;
function Add( x, y : Integer ) : Integer;
begin
 Add := x + y
end;

function Add( s, t : String ) : String;
begin
 Add := Concat( s, t )
end;