A special relationship where each input has a single output.
It is often written as "f(x)" where x is the input value, but can be in other forms.
Example: f(x) = x/2
In words: "f of x equals x divided by 2"
It is a function because each input "x" has a single output "x/2":
• f(2) = 1
• f(16) = 8
• f(−10) = −5
• etc...
