In common use the term translation refers mainly to translating from one language to another. In the case of the transfer referred to in this paper, it is the type of translation within the same language, seen as a way to interpret the linguistic signs using other signs in the same language. The specialized discourse is based on hypothetic-deductive complex structures, while the didactic discourse aims at constructing a descriptive definite picture. The Scientific Research Institutions produce through research scientific knowledge which, by means of translation, through intra-linguistic translation, is then made available to the School for their teaching and learning. One of the discursive procedures through which the transfer of knowledge is made is the definition. Being a basic component of didactic text-discourse, the definition has structure and content determined by the context, being a reformulation, a transposition of the scientific definition. In this paper we aim to highlight the way in which the scientific definition differs from the didactic one by means of discursive analysis on some sub-corpuses of didactic text-discourse. Finally we note the necessity of translating, reformulating the scientific discourse, so that the educational content is transmitted to the student-recipient.