a psychological syndrome noted in partners or relatives of persons with alcohol or drug addiction. Not a formal psychiatric diagnosis, codependency has come to be a useful term for discussing aspects of family dysfunction, particularly among participants in recovery groups like Alcoholics Anonymous and Al-Anon.

Codependency refers to an extreme dependency of one person on another who suffers from an addiction. The dependent person's actions unintentionally help maintain the other person's addictive behaviour—a phenomenon also referred to as “enabling.” Characteristics of codependent persons include low self-esteem, an unreasonably high need for approval and affection, and denial—both of their own personal needs and of problems within the family. Codependent persons tend to enter relationships that are unstable and that leave them vulnerable to exploitation.

In clinical literature, codependency is said to develop from a person's childhood attempts to adapt to dysfunctional family life—e.g., life in which parenting is abusive, neglectful, inconsistent, or otherwise seriously ineffective. The development of dependent strategies is one response to such a situation; dependency becomes the child's way of meeting needs for affection or approval.