Pain is a complex sensation that is not unlike a feeling. Pain is always subjective. It cannot be measured, proven or refuted. In the 1970s, the International Association for the Study of Pain came up with an official definition for pain that applies to both acute and chronic pain, and takes into account the precepts of the biopsychosocial model of illness.
“Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” This model asserts that pain and illness are not always caused exclusively by physical changes, but that dysfunctions and emotional, mental and social problems and disorders can just as easily bring them into being.