This picture shows a hierarchy of classes. It shows that "Ford is-a automobile," "Nissan is-a automobile," and that "VW is-a automobile." It also shows that "Sentra is-a Nissan."
In a hierarchy, each class has at most one parent but might have several children classes. The class at the top of the hierarchy has no parent. This class is called the root of the hierarchy.
Is Nissan a child of Automobile?
Is Nissan the parent of Sentra?