What is a method in an object-oriented language?

In object-oriented programming, a method refers specifically to a function that is defined within the context of a class. This function operates on the data contained within that class and is invoked on instances of that class (often referred to as objects). By defining methods, classes encapsulate behaviors that are relevant to the objects they create.

Methods can take parameters and return values just like regular functions, but they also have access to the instance's attributes and can modify the object's state. This encapsulation of functionality along with data is a fundamental aspect of object-oriented programming, enabling better organization of code and promoting reusability.

The other options do not accurately capture the concept of a method within an object-oriented language. A variable defined inside a class refers to an attribute or property of the class, while a class that inherits from another class describes the relationship between classes (inheritance) rather than a specific function. An instance of a class refers to an object created from that class, which, while it can invoke methods, does not define what a method is. Thus, recognizing a method as a function within a class is pivotal to understanding how object-oriented programming operates.