## Definition 1.2.2: Function, Domain, and Range

Let

**A**and**B**be two sets. A**function***f*from**A**to**B**is a relation between**A**and**B**such that for each*a***A**there is one and only one associated*b***B**. The set**A**is called the**domain**of the function,**B**is called its**range**.
Often a function is denoted by *y = f(x)* or simply *f(x)*,
indicating the relation *{ (x,f(x)) }*.