Outline

Outline is defined by the book as "the edge of a shape or figure depicted by an actual line drawn or painted on the surface. The picture below does a good job of showing what an outline is and how it can be used in art.

This is "Figure 1" and it is a lithograph on wove paper made by Jasper Johns in 1968. The reason that this is a good example of outline is because the number one is clearly outlined, making it stand out from the background, giving it a distinct shape by a physically drawn line.