s-Cis

S-Cis Definition:

A conformation of a conjugated diene in which the disposition of the two p bonds with regard to the connecting single bond is cis-like (a dihedral angle of 0°).

S-Cis Explained:

(S) standing for single. Rotation around a single bond occurs readily, while rotation around a double bond is restricted. The pi bond prevents rotation because of the electron overlap both above and below the plane of the atoms.