What does a chemical dependency mean?

Dependency vs addict: The terms "dependency" and "addiction" are often used interchangeably, but this is incorrect. With dependency, the body exhibits a change when the substance is withheld. This could be something as serious as seizures with alcohol withdrawal or a "simple" as blood pressure going up in absences of anti-hypertensive. Addiction is the continued use despite adverse consequences.

Addiction: Chemical dependency is defined by having a number of symptoms that are related to the use of substance, whether alcohol or other drugs. Inability to stop using, using more than intended, causing harm in your life, taking over your life, as well as physical dependency (tolerance and withdrawal) are part of the syndrome. The new definition (dsm-5) requires at least 3 out of 11 symptoms of dependence.