Stereoisomeric olefins or cycloalkanes (or hetero-analogues) which differ in the positions of atoms (or groups) relative to a reference plane: in the cis-isomer the atoms are on the same side, in the trans-isomer they are on opposite sides., Stereoisomeersed alkeenid ja tsükloalkaanid, mis erinevad aatomite või aatomigruppide asetuse poolest mingi tasandi või ahela suhtes