Bailly
ας (ἡ) c. συνεδρία, PHILOD. V. Herc. 1, p. 18 ; ARSTT. H.A. 9, 2, 1 ; Eud. 7, 2 ; DC. 55, 3 ; 58, 10.
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LSJ
ἡ, sitting as σύνεδροι or in conference, session, meeting, Aeschin. 3.93, 94, SIG 330.34 (Ilium, iv BC), PFrankf. 7v. 14 (iii BC), PTeb. 43.30, 61 (b).223, 72.155, 171 (ii BC); ἀποχωροῦντα ἀπὸ τῆς σ. withdrawing from the circle of friends, X. Mem. 4.2.3; ἡμετὰ τῶν φίλων σ. his conference with his friends, Plb. 18.54.2; παρακληθεὶς ἐπὶ συνεδρείαν Phld. Vit. p. 31 J. ; coupled with συμβουλή, Vit.Philonid. p. 10 C. ; sitting of the Roman Senate, D.C. 55.3.
tenure of office of σύνεδρος, OGI 504.7, 507.11 (Aezani, ii AD). v. συνεδρία. (Written -ία in X. and Aeschin. ll. cc., SIG l.c. (gen. pl. -ιων), Phld. Rh. 1.378 S., but -εία in other Pap. from iii BC, also OGIll. cc. and codd. of Plb. and D.C. ll.cc.)
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
Pape
ἡ, = συνεδρία, von συνεδρεύω, Beratschlagung, μετὰ τῶν φίλων Pol. 18.37.2.
Pape, Griechisch-deutsches Handwörterbuch (3. Aufl., 1914)