* Hair: Cats have fur, which is a defining characteristic of mammals.
* Warm-blooded: Cats maintain a consistent internal body temperature, unlike reptiles or amphibians.
* Give birth to live young: Cats don't lay eggs, they give birth to live kittens.
* Mammary glands: Female cats have mammary glands, which they use to nourish their young with milk.
* Three middle ear bones: Mammals have three bones in their middle ear (malleus, incus, and stapes), which helps with hearing.
* Four-chambered heart: Cats have a four-chambered heart, like all mammals.
These are just some of the key features that make cats mammals.