All objects belong to some class and an object is an instance of the class of which it belongs. Inheritance and Delegation Smalltalk class relationships are defined in terms of inheritance. In inheritance, the inheriting class is called the subclass and the class being inherited from is call the superclass. A subclass inherits all of its superclass' variables and methods. Instances can be implemented any non-abstract class.
Subclasses are specialization of their superclasses.
A subclass may add variables, but it cannot delete those inherited from the superclass. Object instances are instances of a class. The most common relationships in Smalltalk are the inter-class relationships defined by the inheritance class hierarchy. In addition, an object is related to another object when it has a pointer to that object. This serves the need to link objects together and coordinate the behavior between them.