State and explain the conditions for cis/trans isomerism and how this differs from E/Z isomerism.

cis/trans isomerism requires a double bond for restricted rotation about the bond, two different groups on each carbon of the double bond and at least one of the groups on each carbon of the double bond are the same. E/Z only differs by the fact that the isomers can be assigned E or Z as long as all groups attached to each carbon of the double bond are different and a double bond is still required.