a. A condition involving use of a substance, such as a drug or alcohol, or engagement in a behavior, such as gambling, in which a person has strong cravings, is unable to stop or limit the activity, continues the activity despite harmful consequences, and experiences distress upon discontinuance: a drug used in the treatment of heroin addiction.

b. An instance of this: a person with a sex addiction.

a. The condition of being habitually occupied with or involved in something: addiction to romance novels.

b. The condition of using something on a regular or dependent basis: fossil fuel addiction.

c. An instance of one of these conditions: had an addiction to fast cars.