Acute pain is in most cases self limiting, and usually the result of an injury to the tissue. It serves as a warning of disease or a threat to the body. It should be treated aggressively, because it can be severe. Pain lasting longer than several weeks is considered chronic.
Chronic pain serves no useful function to the body.
Chronic malignant pain is associated with a malignant disease such as carcinoma, and chronic non-malignant pain could be caused by many of the same mechanisms but is associated with a malignant disease. Therapy of chronic pain often emphasizes side effects, since treatment may be life-long. It is usually self limiting and it has a beginning and an end. It is not always associated with the severity of disease. Pain has no apparent beginning or end.