Inches, pixels, points, and feet are examples of dimensions of size. Size is simple, but size is more interesting when being referred to in scale. Scale is the contrast of different size objects to each other or to the standard size. Anytime you make a relative comparison between object you have scale.
Scale can be use to show importance and emphasis certain elements. A lack of scale creates competition between elements and leaves the viewer to determine their own entry point into a composition. Elements compete for attention with a lack of scale.
In the assignment following we applied the above information. On the bottom left we created cereal boxes and on the right we created quote designs.