This class diagram contains three subclasses: Duck, Fish, Horse, and one superclass: Animal. Each subclass is connected to the Animal superclass with an inheritance relationship.
Animal inheritance diagram code in Gleek
About class diagrams
Class diagrams are used in software engineering to describe the structure of a system. A class diagram uses Unified Modeling Language (UML) to show the classes, attributes, methods (or operations), and their relationships to each other in the system. Class diagrams prove valuable in object-oriented modeling. Class diagrams can be used to model the data structure or to design a system in detail.