The term arm refers specifically to the segment between the shoulder and the elbow,while the segment between the elbow and wrist is the forearm. However, in common and historical usage, arm refers to the entire upper limb from shoulder to wrist.
Arms are richly adapted for skilled and manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the presence of two forearm bones which can rotate around each other allows for additional range of motion at this level.
Problems in the arm can arise from a wide range of areas; muscle, bone, blood vessels, nerves, the neck or internal organs.