Pain is an intensely unpleasant sensory and emotional awareness that signals threat or damage to the body or that is experienced as bodily injury. Pain is acute if it accompanies an injury or a disease of limited duration. Acute pain disappears with healing. Pain is chronic when it lasts beyond the healing of damaged tissue, is associated with a chronic disease, or persists indefinitely with no apparent cause. Acute pain sometimes provides a protective function, but chronic pain serves no apparent purpose.