A mammal, (class Mammalia), is any vertebrate animal whose young are fed milk from the mother's particular mammary glands.
In addition to their distinctive milk glands, animals have a number of additional distinguishing characteristics.
Vertebrate creatures are classified as mammals. Rats, cats, dogs, deer, monkeys, apes, bats, whales, dolphins, and humans are examples of mammals.
Mammals are vertebrates that have hair, milk-producing mammary glands, a diaphragm, three bones in the middle ear, and a lower jaw made up of a single set of bones that articulates with the skull in a unique way.
Humans are classed as mammals because they share the same distinguishing characteristics (mentioned above) as the rest of this vast group.