Basic Definitions & Clinical Implications

In this session, you will learn basic pain-related definitions and review pain physiology. This information is critical to understanding the complex nature of the pain experience and the rationale behind various treatment strategies.

Pain Terminology:
For a list of definitions of terms used in pain management see:

Pain (International Association of the Study of Pain)


An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Pain is subjective. Each individual learns the meaning of the word "pain" through experiences related to injury in early life. Biologists recognize that those stimuli or illnesses that cause pain are likely to damage tissue. Accordingly, pain is an experience we associate with actual or potential tissue damage. Pain is always unpleasant and therefore an emotional experience.

 Implication for Clinical Practice 

There is no physiological, imaging, or laboratory test that can identify or measure pain. Pain is what the patient says it is. The clinician must accept the patient's report of pain.


Making a Distinction Between Pain and Nociception


Pain is a conscious experience that results from brain activity in response to a noxious stimulus and engages the sensory, emotional and cognitive processes of the brain. In general terms we can distinguish two dimensions or components of pain: (a) sensory-discriminative and (b) affective-emotional.

Nociception is the process by which information about a noxious stimulus is conveyed to the brain. It is the total sum of neural activity that occurs prior to the cognitive processes that enable humans to identify a sensation as pain. Nociception is necessary but not sufficient for the experience of pain.

 Implication for Clinical Practice 

The goal of pain therapies is to relieve pain whenever possible: from nociception to the conscious experience as well as to decrease the emotional response to the unpleasant experience. Nociception should be treated even in unconscious patients who appear to be clinically unresponsive to pain to help prevent sensitization of pain pathways which can lead to chronic pain.