prefix (opp. TRANS- or ULTRA-). 1 on this side of; on the side nearer to the speaker or writer (cisatlantic). 2 Rom. Antiq. on the Roman side of (cisalpine). 3 (of time) closer to the present (cis-Elizabethan). 4 Chem. (of an isomer) having two atoms or groups on the same side of a given plane in the molecule.
[ L cis on this side of ]