Why is a mamal a mamal?

Mammals are classified as mammals primarily because they possess specific characteristics that distinguish them from other animal groups. These include having mammary glands that produce milk for their young, fur or hair on their bodies, and three middle ear bones that aid in hearing. Additionally, mammals are warm-blooded, have a more complex brain structure, and typically give live birth, with few exceptions like monotremes. These traits collectively define mammals within the animal kingdom.