LSJ
one must divide or distinguish, Pl. R. 412b, Lg. 874e, Porph. Abst. 2.38; δίχα δ. Pl. Sph. 265a; τινὰς ἀπ’ ἀλλήλων Id. Plt. 287b; διαιρετέον πόσαι διαφοραί Arist. Pol. 1289b12.
one must open a vein, Antyll. ap. Orib. 7.2 tit., Aët. 16.90.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)