Pain is one of the body’s most important communication tools; it is a way to tell us something is wrong.
A warning mechanism that protects us by warning us of illness, threat or injury, pain is a complicated mixture of physiological and psychological response.
In general, people do not like pain. In fact, pain is the most common reason for doctor visits. A dictionary defines pain as "suffering or distress of body or mind; also: a basic bodily sensation marked by discomfort (as throbbing or aching)". Therefore, it is an unpleasant physical and emotional experience. Pain is one of the body's most important communication tools; it is a way to tell us something is wrong. Pain has multiple causes, can last a brief, intense period, or persist for a long time.
As a communication tool, pain tells a person to cease activities, to protect an injured area, and to avoid repeating damaging activities. Normally, pain stops when the painful activity stops and the body has recovered. Occasionally, pain continues after an activity has ceased and the body appears to have healed. There are times when a person experiences pain without knowing the cause. Pain, regardless of whether the cause is known or unknown, can adversely affect a person's quality of life, as well as reduce their functional ability.
Pain is a complex phenomenon and there are many ways to classify it. There is disagreement among experts as to the best way to classify pain. One way pain can be classified is by the area affected (e.g., muscular or joint pain). A common starting point is to classify pain by length of time as either acute or chronic/persistent pain.
The traditional dividing line between acute and chronic pain is based on the length of time from onset. Three and six months from the onset of pain are the two most used time points to divide acute from chronic pain. Although both acute and chronic pain can be physically and emotionally debilitating, chronic pain (due to its persistence) can have more profound consequences for a patient.
Pain may also be classified by its pathophysiology (by the kind of damage that causes it) as either nociceptive or neuropathic pain. Due to the complexity of pain, it may not easily be categorized in an "either/or" sense and may in fact fit in multiple categories simultaneously.