Fifteen chapters focusing on definitions, e.g., fire, silver. In the Syriac version published by Muyldermans in 1952 (pp. 88-89 comments; 130-33 ed.; 160-63, trans.), numbering begins with 27, after Reflections (CPG 2433) and On Perfection (CPG 2476). Although classified as dubia/spuria in the CPG, these may be authentic, given that many Greek fragments survive in the Byzantine definition collections. Manuscripts: BL Add. 17167, BL Add. 17192 (no title), BL Add. 12175 (missing title and first keph.), BL Add. 14578, BL Add. 14621, 7190 Rich. (missing first eight keph.)