ON THE GEOMETRICAL TERM RADIUS IN ANCIENT LATIN

Abstract

According to major Latin dictionaries, the word radius is attested as a terminus technicus for the geometrical concept ‘radius’ in Cicero’s Timaeus 17. In this study, however, it is argued that there is good reason to believe that Cicero did not use the word in this sense, but in a metaphorical expression in which radius mainly carries the well-attested sense of ‘rod (for drawing diagrams, etc.)’: paribus radiis attingi literally = ‘to be touched by equal rods’, that is to say, ‘to be equidistant’. The first and only convincing attestation of radius in the sense of ‘radius (of a circle, sphere, etc.)’ in ancient Latin literature is found in Calcidius’ Commentaryon the Timaeus 59. It is suggested that Calcidius was influenced by Cicero’s translation and consequently adopted the word radius; however, its technical sense of ‘radius’ was coined, deliberately or not, by Calcidius himself. As there are no other convincing attestations of this sense of the word in ancient Latin, not even in geometrical texts, it is suggested that the word radius never became a commonly accepted terminus technicus for radius in antiquity.