addiction

n. A dependence on a drug or other substance, especially one in which the person feels pleasure or release from tension in using the substance and anticipates negative future consequences from its use, as in cigarette smoking. Previously the term denoted a physiological dependence in which the person needed increasing doses to reach a given level of reaction (tolerance) and unpleasant and sometimes dangerous consequences when the substance was withdrawn. However, governmental agencies have continuously expanded the use of the term for political purposes so that the term addiction is now used in a much broader sense and people speak of being addicted to chocolate or exercise, which produce high levels of bodily chemicals associated with pleasurable sensations.