A function is only a function of the input (X) has one and only one output (Y). So in this case, every input has only one output as there are no X values that have two or more Y values so this is a function. However if we are given a set of points like (6,8) (3,2) and (6,20) we can determine its not a function because when X equals 6, Y could equal 8 or 20.