Define the concept of polymorphism in programming languages.

Polymorphism in programming languages refers to the ability of a variable, function, or object to take on multiple forms.

In more detail, polymorphism is a fundamental concept in object-oriented programming (OOP) that allows objects of different types to be treated as objects of a common, more general type. This concept is derived from the Greek words 'poly' meaning many, and 'morph' meaning forms. Hence, polymorphism is about 'many forms'.

There are two types of polymorphism: compile-time (or static) and runtime (or dynamic). Compile-time polymorphism is achieved through function overloading and operator overloading. Function overloading allows multiple functions with the same name but different parameters, while operator overloading allows redefining the way operators work with user-defined types.

On the other hand, runtime polymorphism is achieved through inheritance and interface. Inheritance allows a child class to inherit properties and methods from a parent class, and an interface defines a contract for what a class can do, without saying anything about how the class will do it.

Polymorphism is beneficial in programming because it promotes flexibility and reusability. It allows one interface to be used for a general class of actions, and the specific action is determined by the exact nature of the situation. For example, consider a 'shape' class with a method called 'draw'. This method will behave differently depending on whether the shape is a circle, square, triangle, etc. But the user doesn't need to know which type of shape they're dealing with - they just call the 'draw' method and the correct action is taken based on the type of shape.

In summary, polymorphism is a powerful tool in programming that allows for flexibility and reusability by enabling a single interface to represent a general class of actions. It's a key concept in object-oriented programming and is used extensively in many programming languages.