A flow chart is a graphical representation of a relation between two variables, connecting input and output values with lines or arrows.
A relation is any set of ordered pairs . A relation can have more than one output for a given input.
vertical line test
The vertical line test is a visual method of determining whether a graph of a relation is a function. The test determines that the relation is a function when no vertical line intersects the graph at more than one point.
A function is a relation where there is only one output for every input. In other words, for every value of , there is only one value for .
Learn how to determine whether or not a relation is a function.