Define and identify relations and functions
Since we can write related quantities using ordered pairs, a set of ordered pairs such as
{(5, 40), (10, 80), (20, 160), (40, 320)}
is called a relation.
Relation
A relation is any set of ordered pairs.
A special kind of relation, called a function, is very important in mathematics and its applications.
Function
A function is a relation in which, for each value of the first component of the ordered pairs, there is exactly one value of the second component.