παρασκήν-ιον · paraskēn-ion — LSJ
side-scene, τῆς λιθείας τῆς εἰς τὸ π. IG ΙΙ(2).203A 88 (Delos, iii B. C.) : elsewh. in pl., D. 21.17, IG ΙΙ(2).199A 91 (Delos, iii B.C.), al. ; ἐν τοῖς π. cj. for ἐν τοῖς προσκηνίοις in Alciphr. 2.4.
in sg., use of one of the chorus as a fourth actor, Poll. 4.109.