Concept inclusion constitutes a kind of imperfect equivalence in translating that gives rise to a 1:2 terminological relation and that represents an important translation problem. In translating scientific texts in the fields of biology or medicine into Spanish or Portuguese one such case of concept inclusion is that brought about by the (frequent) usage of the words brain , in English, and (Ge)hirn , in German (whose proper meaning is ‘encephalon’), as generic terms , i. e., as referring to structures or processes that take place exclusively within the cerebrum (therefore, as synonyms of, respectively, cerebrum and Großhirn or Cerebrum ). Currently, through the undue calque of this phenomenon, many scientific texts written in Spanish or Portuguese and translated from English or (to a lesser degree) from German show the unidiomatic usage of the word encéfalo , which means ‘encephalon’, as a generic term (which causes a remarkable strangeness effect, especially in popularizing texts), or, even more frequently, they improperly and deceively use the term cerebro / cérebro (which means ‘cerebrum’) to refer to the encephalon as a whole. In order to avoid this harmful interference, in rendering brain and (Ge)hirn into Spanish or Portuguese the translator of a scientific text should strive to discriminate (with resort to adequate documentation) between occurrences of the word in its proper sense and occurrences of the word as a generic term . Based on the analysis of a number of author-made translations into Spanish (and Portuguese) of passages of English and German-language encyclopedic articles, popularizing books and popularizing articles with scientific content, the present study aims to define the most adequate translation strategy for the problem described, which can be summarized in the three following cases: a ) usage of brain or (Ge)hirn in its proper sense (with extracerebral referents), translated as Sp. encéfalo , encefálico , intracraneal (Port. encéfalo , encefálico , intracraniano ); b ) usage of brain or (Ge)hirn as generic terms (with exclusively cerebral referents), translated as Sp. cerebro , cerebral (Port. cérebro , cerebral ); c ) usage of brain or (Ge)hirn as generic terms (with exclusively cerebral referents), but not directly translatable as Sp. cerebro , cerebral (Port. cérebro , cerebral ) owing to the occurrence in the source text of data pertaining to the encephalon as a whole (in this case, the translator should assess the possibility of using in the target text cerebro / cérebro for all occurrences—by adapting the original data—, or, at least, complementarily with encéfalo —by departing from the original wording).