In this workshop we hope to show how, for a proper understanding of medieval translations of medical works into Arabic, Latin and Hebrew, one must in many cases go back to the original source of the text in question. This is the case where the translator employs the technique of loan-translation (calque) and especially that of ‘semantic borrowing’, i.e. to give words and terms a new, extended meaning by analogy with a partly synonymous term in the original language. Thus the Arabic ta‘aba (to work hard, to become tired) becomes ‘to suffer from pain’ on the basis of the Greek poneo; likewise the Hebrew yaga‘ or hitrid following the Arabic ta‘aba; and the Latin offendens (striking against) becomes ‘interrupted’ on the basis of the Greek proskoptos. In several cases these extended meanings are missing in the current dictionaries, particularly those of the Hebrew language. We also find unattested, newly coined terms whose meaning can only be retrieved by comparison with the original source. An example is the Hebrew ha-mayim ha-ra‘im (lit. bad water) used for ‘dropsy’ (Latin hydrops); or the Hebrew sibbuv hashukhi (lit. dark turning around) for the Greek skotodinos ‘dizziness’. We will also see that the technical terminology employed by the different translators fluctuates widely—there is no standard terminology. Our examples are derived from the Hippocratic Aphorisms, bks. 4 and 5, in the Arabic translation by Hunayn ibn Ishaq, the Latin translation (from Arabic) by Constantine the African (part of the Articella, ed. 1510), and the Hebrew translations by Moses Ibn Tibbon, Nathan ha-Me’ati, Zerahyah Hen and Anonymous (from Arabic), by Hillel of Verona and Judah Shalom (from Latin), and finally by Joseph Delmedigo from the original Greek text.