So trans is defined the following way. Hydrogens are on different sides of the plane, x and x, I mean H and H different sides. And E is defined as the heavier groups are in different sides. So, once again, our X and Y are in different signs. Now, these two guides are isomers to one another, and they're separated by 66 kilotons of mole. So let's look at the following few examples, and let's try to figure out which ones are E and which ones are Z.