ἰδιομήκης
From LSJ
ἀμήχανον δὲ παντὸς ἀνδρὸς ἐκμαθεῖν ψυχήν τε καὶ φρόνημα καὶ γνώμην, πρὶν ἂν ἀρχαῖς τε καὶ νόμοισιν ἐντριβὴς φανῇ → hard it is to learn the mind of any mortal or the heart, 'till he be tried in chief authority | it is impossible to know fully any man's character, will, or judgment, until he has been proved by the test of rule and law-giving
English (LSJ)
ες,
A of their own length, i.e. of the same length each way, of square numbers, Nicom.Ar.2.18.
German (Pape)
[Seite 1236] ες, von eigener Länge; von Zahlen, wie 4 = 2. 2, Nicom. arithm. 2, 18.