In terms of geometric isomers, what does 'Z' and 'E' represent?

In the context of geometric isomers, 'Z' and 'E' designate the configurations around a double bond based on the positions of substituent groups.

The 'Z' configuration, derived from the German word "zusammen," indicates that the higher priority substituents on the double-bonded carbons are on the same side of the double bond, leading to a configuration often synonymous with "cis." Conversely, the 'E' configuration, coming from "entgegen," indicates that the higher priority substituents are on opposite sides, analogous to a "trans" configuration.

This system of notation is particularly useful for alkenes where the traditional cis and trans terminology may be insufficient, especially when dealing with more complex molecules where there are multiple substituents. Therefore, the correct answer accurately represents these definitions of geometric isomers.