There is active scientific debate about the nature of addiction as a mental disorder, but typically with little discussion of clinical definitions in contemporary nosology. To contribute to the ongoing dialogue, this review provides a concise history of the medical diagnoses used to define the natural language concept of addiction in clinical terms, beginning at the inception of the two most widely used classification systems: the International Classification of Diseases and Diagnostic and Statistical Manual (DSM). Across systems, the evolving nosology can be heuristically divided into three epochs: a primeval period (1900-1948), reflecting coarse definitions subsumed within personality disorder; a descriptive period (1948-1980), reflecting increasingly phenomenological and descriptive definitions; and an empirically-informed period (1980 to the present), reflecting operational definitions reflecting polythetic syndromes with empirical substantiation using modern empirical techniques. Over time, definitions have consistently moved away from moral and personality-based models toward more person-centred and non-stigmatizing perspectives. Tracing the vicissitudes of clinical definitions of addiction over the past century reveals an evolution that is both more scientific and humane. Contemporary priorities include incorporating objective indicators reflecting causative and maintaining mechanisms to increase the alignment between diagnosis and etiology.