 Defining death is one thing; providing criteria by which it can be readily detected or verified is another. A definition is an account of what death is; when, and only when its definition is met, death has necessarily occurred. A criterion for death, by contrast, lays out conditions by which all and only actual deaths may be readily identified. In some cases criteria for death are intended to capture conditions by which the actual deaths of human persons may be identified. Such a criterion falls short of a definition, but plays a practical role. For example, criteria for the death of a person would help physicians and jurists determine when death has occurred.