There are several forms of inheritance: single inheritance, multiple inheritance, repeated
inheritance, and selective inheritance. Figure 25.5 shows an example of single inheritance,
where the subclasses Manager and SalesStaff inherit the properties of the superclass Staff.
The term ‘single inheritance’ refers to the fact that the subclasses inherit from no more
than one superclass. The superclass Staff could itself be a subclass of a superclass, Person,
thus forming a class hierarchy.