What defines an abstract class?

An abstract class is defined as a class that is declared without a complete implementation and includes one or more abstract methods. Abstract methods are methods that are declared but do not have any implementation in the abstract class. This means that the abstract class serves as a blueprint for other classes, which must provide concrete implementations of the abstract methods when they inherit from the abstract class.

This characteristic allows for a level of abstraction in programming, enabling developers to define general behaviors that can be shared among multiple derived classes while still enforcing that specific methods are implemented in those subclasses. The abstract class itself cannot be instantiated directly, which emphasizes its role as a base or template for other classes rather than a standalone functional component.

This definition encompasses the fundamental purpose of abstract classes in object-oriented programming, where they promote code reusability and polymorphism by allowing specific implementations to be defined in subclasses.