NANDA: The state in which an individual experiences and reports the presence of severe discomfort or an uncomfortable sensation.
  A highly subjective state in which a variety of unpleasant sensations and a wide range of distressing factors may be experienced by the sufferer. Pain may be acute, a symptom of injury or illness such as a myocardial infarction, or chronic, lasting longer than 6 months, the result of a long-term illness such as arthritis. Pain may also arise from emotional, psychological, cultural, or spiritual distress. Pain can be very difficult to explain, because it is unique to the individual; pain should be accepted as described by the sufferer. Pain assessment can be challenging, especially in the elderly, where cognitive impairment and sensory-perceptual deficits are more common.