Isaac of Nineveh, best known in the Slavic tradition as Isaac the Syrian, was a prominent figure in Eastern Christianity whose works were quickly translated into other languages. The two known medieval South Slavic translations were accomplished from Greek; the second one became particularly popular among the East Slavs and spread widely in that region. Isaac’s teachings found a large audience in monastic circles and were often included in miscellanies. This paper aims to analyse the language used to address the intellectual and noetic realms in the Slavonic translations of Isaac’s works. To this end, sections of the unedited Slavonic text have been prepared for comparison with the original Greek. This terminology is then be compared with translation equivalents found in other ascetic works in Slavonic. Apart from the linguistic aspect, the study also attempts to trace the influence of language on the transmission of ideas through translation. As an appendix, an edition of one sermon is presented for the first time, with the two known Slavonic versions printed side by side alongside the Greek text with critical apparatus and comments on the translation features.