What is polymorphism in object-oriented programming?

In object-oriented programming, polymorphism refers to the ability for an object to be treated as an instance of its parent class or any of its ancestor classes up through its inheritance chain. This means that the same method name can refer to different functions depending on the object’s actual type during runtime. For example, if a class Dog inherits from a class Animal, a Dog instance can be treated as an Animal. This supports code flexibility and reuse, allowing developers to write more general and high-level code without needing to specify the exact types of objects being manipulated.

In polymorphism, when a method is called on an object, the appropriate method for the specific object's type will execute. This dynamic method resolution is a core concept that facilitates implementing design patterns such as Strategy and Command patterns, making code more modular and maintainable.

The other options describe different OOP concepts that do not directly pertain to polymorphism. For example, the ability for an object to have multiple states relates more to state management. The ability to hide complexities from the user corresponds to encapsulation, and the ability to create a variable that can hold multiple types of data pertains to type variance, not specifically to polymorphism.