To create a subclass is specialization, to factor out common parts of derived classes into a common base (or parent) is generalization [Booch 91, p56]. Overriding is the term used in Smalltalk and C++ for redefining a (virtual in Simula and C++) method in a derived class, thus providing specialized behaviour. All routines in Smalltalk are overridable and non- "frozen" features in Eiffel can be "redefined" in a derived class. Whenever a method is invoked on an object of the base class, the derived class method is executed overriding the base class method, if any. Overriding in Simula is a combination of overloading and multiple-polymorphism because parameters do not have to be declared. Eiffel and BETA are examples of languages allowing any member to be redefined and not just methods, as is typical.   _{Your Comment}