How can you tell if a graph is function or not​

Step-by-step explanation:

For a graph to be a function, there must not be more than one element in the range for each element of the domain.

If x represents the doman, and y represents the range (as usual, in graphing) then each value on the the x-axis should not have more than one point in the graph on it, directly above it, or directly below it. Like if you had a point (5, 7) and also had point (5, -7), that is not a function. The x, 5, has more than one y-value  paired with it.

Visually, any vertical line through the graph should not intersect the graph at more than one point. If it does, then the graph is not a function.

This is called the vertical line test.

I have attached a graphic.