Define the term "interface" in OOP.

The term "interface" in object-oriented programming (OOP) refers to a contract that a class can implement, defining a set of methods without providing any implementation details. An interface specifies what methods a class must have but does not dictate how those methods should be executed. This provides a way to enforce certain capabilities across different classes, promoting a level of abstraction and enabling polymorphism.

When a class implements an interface, it is agreeing to provide concrete implementations for all of the methods defined in that interface. This concept allows for increased flexibility and interoperability among classes, as different classes can implement the same interface in various ways. The use of interfaces helps developers create more modular and maintainable code, as it decouples the definition of operations from the actual implementation.

In contrast, the other options inaccurately describe what an interface is. An abstract class, while somewhat related, provides partial implementation and may include member variables, unlike an interface which purely defines method signatures. Access control mechanisms relate to encapsulation rather than defining method contracts. Lastly, the concept of a derived class that inherits from multiple classes is more aligned with multiple inheritance, which is not the function or purpose of an interface.