2. to be a colleague or partner in office, c. dat., Th.7.31: ὁ συνάρχων colleague in office, Id.6.25, 8.27, Lys.12.52, Pl.R.463b, freq. in Inscrr., IG12.304.6, al.; “στεφανοῦσθαι ὑπὸ τῶν συναρχόντων” Hyp.Lyc.16; “τῶν τούτου συναρχόντων” Lys.12.79.
2. begin at the same time as, c. dat., Phlp. in de An.588.4.