A very common name, so the particular bearer of it who generated this entry is unknown. But the most likely candidate, arguably, is D. of Alexandria, the celebrated hellenistic-period mathematician (OCD(4) p.465; biography at web address 1). His works surviving in Greek are normally cited in page numbers from the Teubner edition by Tannery in 2 volumes (1883, 1885). The important new edition by Roshdi Rashed in progress since 1984 in the Budé series, with facing-page translation in French, is also based on the ancient Arabic translation of his work. (The history of the relationship between Greek and Arabic algebra is the focus of important contemporary work in rewriting the history of mathematics.)
For this Diophantos see under upsilon 166 (Hypatia's commentary on his work). For homonyms see under delta 1491, lambda 486, mu 462, pi 1617.