Overlapping

Interposition
If we move the two forms still closer, one crosses over the other and appears to remain above, covering a portion of the form that appears to be underneath. [Wong, Wucius. Principals of Two-Dimensional Form. New York: Van Nostrand Reinhold Company, 1988.]

Spatial Effect:
It is obvious that one form is in front of or above the other. [Wong, Wucius. Principals of Two-Dimensional Form. New York: Van Nostrand Reinhold Company, 1988.]

Interrelationships of Form
Forms can encounter one another in numerous ways . . . . when one form crosses over another, the results are not as simple as . . . . [one may think].

Take two circles and see how they can be brought together. We choose two circles of the same size to avoid unnecessary complications. Eight different ways of interrelationship can be distinguished;

1) Detachment. The two forms remain separate from each other although they may be very close together.

2) Touching. If we move the two forms closer, they begin to touch. The continuous space which keeps the two forms apart in the example of detachment is thus broken.

3) Overlapping. If we move the two forms still closer, one crosses over the other and appears to remain above, covering a portion of the form that appears to be underneath.

4) Penetration. Same as overlapping, but both forms appear transparent. There is no obvious above-and-below relationship between them, and the contours of both forms remain entirely visible.

5) Union. Same as overlapping, but the two forms are joined together and become a new, bigger form. Both forms lose one part of their contours when they are in union.

6) Subtraction. When an invisible form crosses over a visible form, the result is subtraction. The portion of the visible form that is covered up by the invisible form becomes invisible also. Subtraction, may be regarded as the overlapping of a negative form on a positive form.

7) Intersection. Same as Subtraction, but only the portion where the two forms cross over each other is visible. A new, smaller form emerges as a result of intersection. It may not remind us of the original forms from which it is created.

8) Coinciding. If we move the two forms still closer, they coincide. The two circles become one. The various kinds of interrelationships should always be explored when forms are organized in a design.