It has become impossible in practice, and is scientifically unsound, to maintain a single definition for all forms of drug addiction and/or habituation. A feature common to these conditions as well as to drug abuse in general is dependence, psychic or physical or both, of the individual on a chemical agent. Therefore, better understanding should be attained by substitution of the term drug dependence of this or that type, according to the agent or class of agents involved, in discussions of these conditions, especially inter-disciplinary. Short descriptions, followed by concise listings of their characteristics, are formulated for the various types of dependence on at present widely abused major groups of substances.