Medical professionals and those working in the study of alcoholism and addiction sometimes use expressions such as “substance abuse” or “chemical dependency” to interchangeably refer to both alcoholism and drug addiction. Occasionally, these professional, not familiar with the Twelve Traditions of Alcoholics Anonymous, introduce and encourage nonalcoholic persons to attend A.A. meetings. For the nonalcoholic, the Fellowship of A.A. has open meetings which anyone may attend as a welcome guest, but only people that have or think they may have a problem with alcohol may attend closed A.A. meetings.