1. The devotion or the giving oneself habitually, or compulsively, to something; such as, caffeine or alcohol; but especially to narcotics: Harriet's novel emphasized the main character's recovery from drug addiction.
2. The conditions of being overwhelmed or uncontrollably committed to causes or to special objectives: Amy's main addiction is her excess devotion to operas where she spends a great deal of time and expenses attending them as often as possible.

Sally had an addiction for buying clothes, shoes, purses, and other items even though she didn't need them and didn't have enough space to put them where she could access them, as a result, she had very little money for other necessities; such as, food, making her car payments, paying her rent, etc.

3. Situations that involve compulsions and the need to continue taking drugs as a result of taking them in the past: Greg was trying to follow his doctor's advice to stop his crack addiction which he had had for years. Getting away from his old friends, who also had the same addictions, was extremely difficult and hindered him from turning away from that type of life.

For more information, see these compositions: Addicts and Addiction.