Polysemy is a linguistic characteristic common in many languages that enriches oral expression and is the basis of many puns that constitute a big problem for translators of Shakespeare’s plays into Spanish or French. The context, the intonation or companion words usually avoid interpretation mistakes either in oral or written language. Additionally, nowadays polysemy can be problematic for data mining and medical studies based on databases containing clinical information of patients, up to the point of threatening their usefulness for specific purposes. One example is “drugs”. InPhaedrus, Plato cites the Greekword “pharmakon” and describes its different meanings (“remedy”, “poison” and “drug or philtre”—either for good or bad purposes Q1 ). The text also explains that sometimes beneficial or harmful effects of a pharmakon depend on the administered dosage.1 Later, pharmacology took that Greek root and was used to define “the scientific study of drugs and how they are used in medicine”; so “drug”, whose etymology is not well-known, became a common term to refer both, remedies and substances of abuse.2 The word drug has been introduced to designate any natural or synthetic substance able to produce physiologic or psychological alterations, beneficial or not,2,3 thus keeping the original polysemy of pharmakon. According to the definition, aspirin and penicillin are drugs; marihuana and methadone are drugs, too. The uses and effects of these substances are different, and the meaning and consequences of the same word used to designate them can also be completely different. So, “to sell drugs” can be either a perfectly legal activity carried out by pharmacists, or the illegal doings carried out by dealers in dark alleys. Both meanings require a context3 but in certain circumstances, the context is lacking; this is the case of taxonomy systems such as the International Classification of Diseases (ICD).4 The word “drug” appears in 262 ICD-10 codes where polysemy can be a cause of misunderstanding in two different steps of the process: (i) during the codification of diagnoses and symptoms from clinical charts, and (ii) later, when researchers retrieve electronic registers for analyses and studies. Several authors have already attracted attention to problems derived from polysemy in clinical practice (e.g., promoting healthy eating),5 the management and research using scientific databases,6 and automatic translation systems.7 This is a potential problem because research using large databases will increase in the future.