Class

A class is a taxonomic category that groups together related orders — orders that share a set of common features are placed in the same class.

For example, the order Primata (which includes monkeys, gorillas and gibbons) and the order Carnivora (which includes animals such as the tiger, cat and dog) are both placed in the class Mammalia. Even though the animals in these two orders differ in many outward ways, they all share the defining mammalian characters, so they are kept together in one class. Class Mammalia contains several other orders besides these two. …