Monkeys are mammals. Specifically, they are placental mammals, meaning that they carry their young inside a womb until they are developed enough to live independently of their parent.
Monkeys share many features with other mammals. For example, monkeys are covered in hair or fur, have a variety of differently shaped teeth in their jaws and produce milk from mammary glands to feed their young. Monkeys also have some distinct features, such as their paws, that separate them from other mammalian groups. Monkeys have flat nails on their digits rather than claws, and they have thumbs on their paws that allow them to grip tree branches and manipulate small objects.