Definition
Mapping diagram
A mapping diagram places inputs and outputs in separate groups, then connects each pairing with a directed arrow.
What it means
Begin with a value in the input group and trace the arrowhead. Where it lands is that input’s partner. The picture describes a function only if every input starts exactly one arrow; different inputs may land on the same output.
Remember it
Choose an input, trace its arrowhead, and see where it lands.
Example
Use y = 2 × x + 2. Draw 0→2, 1→4, 2→6, and 3→8. Because one arrow begins at each input, the pictured relation is a function.
Watch for
A mapping diagram can show a relation that is not a function. If one input has two outgoing arrows, the diagram format is valid but the function rule fails.
Common mix-up
A function does not require different outputs. Two or more inputs may point to the same output.
Exact meaning
A mapping diagram displays a relation in two labelled sets. Each ordered pair is drawn as a directed connector from its input value to its output value.