A specialized class in a generalization/specialization hierarchy, which contains additional attributes and methods distinguishing it from a more general class that it extends.

One or more classes that are more specific versions of another similar class. A subclass inherits all the attributes and operations of the class it's based on.

If B is a subclass of A, then B is derived from A. This means that B inherits all of the attributes and operations of A, but may also add additional attributes and operations. Other terms that means the same thing are B derives from A, or B extends A.