Interactive Real Analysis
- part of 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.
Context
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)) }.
Context