When data is PROPORTIONAL it:

-Has to start at the Origin (0,0). Y-Intercept is 0.
-Has a constant rate of change (m=y/x)
-Is Linear
-Has an equation in the form of y=mx

When data is NON-PROPORTIONAL it is missing one of the following:
-Does not start at the Origin (0,0). Y-Intercept is not 0.
-Does not have a constant rate of change (m=y/x)
-Linear
-Equation is in the form of y=mx+b