# In this Section:

In this section, we review the basic concept of a function. The basic idea of a function first starts with an understanding of a relation.
A relation is nothing more than any set of ordered pairs. A function is a special type of relation, where each x value corresponds to, or is linked up with exactly one y value. It is often
said that for each ‘x’, there can be only one ‘y’. When we have a function, it is crystal clear what the value is for y, given a certain x value. As an example of something that is not a
function: {(6,2),(3,7),(6,-4)}. We can see in this example, the x value of 6 corresponds to two different y values: 2 and -4. This is a violation of the definition of a function. If we had a
function, the x value of 6 should only correspond to exactly one y value. As an example of a function: {(3,5),(-2,7),(4,12)}. In this case, each x value corresponds to only one y value. The x
value of 3 corresponds to a y value of 5. The x value of -2 corresponds to a y value of 7. Lastly, the x value of 4 corresponds to a y value of 12.