Next, we will look at the “inverse” relation named “Egg Color to Chicken.” Here we consider the color of an egg to be the input, and want the output to be the name of a chicken. If the egg is green, we know it is Emma's. But what if the egg is brown?
In Figure 9.1.8, we can see the color brown (an input) is related to two outputs, Yvonne and Georgia. This disqualifies the relation “Egg Color to Chicken” from being a function. (It is still a relation, because in general knowing the egg color does give you some information about which chicken it may have come from.)