is-a

A relationship between two objects in which one object is considered to be a more specific version of the other, generic object: "A camel is a mammal." Since the generic object really only exists in a Platonic sense, we usually add a little abstraction to the notion of objects and think of the relationship as being between a generic "base class" and a specific "derived class". Oddly enough, Platonic classes don't always have Platonic relationships--see "inheritance".