A limb (from the Old English lim) is a jointed appendage of the human or animal body; a large or main branch of a tree; a representative, branch or member of a group or organization.
Most animals use limbs for locomotion, such as walking, running, or climbing. Some animals can use their front limbs (or upper limbs in humans) to carry and manipulate objects. Other animals can use their hind limbs for manipulation as well.
In the human body, the upper and lower limbs are commonly called the arms and the legs. Human legs and feet are specialised for two-legged locomotion -- most other animals walk and run on all four limbs. Human arms are weaker, but very mobile allowing us to reach at a wide range of distances and angles, and end in specialised hands capable of grasping and fine manipulation of objects.
A limb (from the Latin limbus) is the graduated edge of a circle or arc within an astronomical or surveying intrument. In astronomy, it designates the border or outermost edge of a celestial body. In botany, it designates the border or upper spreading part of a sympetallous corolla or of a petal or sepal.