A "limb" refers to a large, primary appendage of the body, such as an arm or a leg. Limbs are essential for movement and interaction with the environment. In humans, the upper limbs include the arms, while the lower limbs consist of the legs. Each limb is made up of bones, muscles, and joints that work together to allow for a wide range of motions. In addition to humans, many animals also have limbs, which can vary in structure and function. For example, birds have wings as limbs for flying, while dogs have four legs for running and walking. The design of limbs is adapted to the specific needs of each species, enabling them to thrive in their habitats.