# What are the rules for defining E-Z configuration?

This is very reminiscent of the $R$ and $S$ configuration assignments. We find an double bond that has a few different substituents, such as those above.
In the former molecule, it's $Z$ since the highest priority substituents are on the same side of double bond.
In the latter molecules, it's $E$ since the highest priority substituents are on different sides of the double bond.