The passive voice represents the subject as acted on: ἐώθουν, ἐωθοῦντο, ἔπαιον, ἐπαίοντο
a. The passive has been developed from the middle. With the exception of some futures and the aorist, the middle forms do duty as passives: αἱρεῖται
b. Uncompounded ἐσχόμην sometimes retained its use as a passive. ἐσχέθην is late.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].