Which type of class cannot be instantiated?

An abstract class serves as a blueprint for other classes and cannot be instantiated directly. Its primary purpose is to define a common interface for other classes through abstract methods, which must be implemented by any derived classes. The abstract class may contain both abstract methods (which have no implementation) and concrete methods (which do).

Because abstract classes cannot be instantiated, they ensure that a level of abstraction is maintained. This allows for code reusability and promotes a consistent design across various implementations. By forcing derived classes to provide specific implementations of abstract methods, abstract classes facilitate polymorphism and enhance object-oriented programming practices.

In contrast, a static class is also not instantiated in the traditional sense, but its members are accessed statically. Concrete classes can be instantiated and represent objects that can have their own state and behavior. Derived classes are essentially extensions of base classes that may augment or modify their behavior but can still be instantiated if they do not remain abstract.