Not the least noticeable is the fact that the ancient Greek compound euthanasia, formed by Francis Bacon, has retained its original terminological form since it was first used in the 17th century. Among all other controversial (bio)ethical issues, however, the conceptual notion of euthanasia categorically evokes rather important controversies. The questions that arise in this context are whether there is a definition, or at least a determination, of the term euthanasia and whether we are aware of its use in scientific discourse, what exactly is euthanasia. The paper offers a terminological elaboration of the term euthanasia in a linguistic (lexicographic), but mainly legal and medical-procedural context, in order to examine the coherence in defining the term between these categories and, consequently, to determine the key determinants of euthanasia according to categorical sections. The key facts stated are the primary determination or the possible definition of the term for any further scientific study of euthanasia as one of the most controversial issues within bioethical doctrine.