Final answer:
A shape on a flat picture surface defined by surrounding empty space is called a negative shape. It is the area around and between the positive shapes in a composition.
Step-by-step explanation:
A shape on a flat picture surface that is defined by surrounding empty space is known as a negative shape. This contrasts with a positive shape, which is delineated by its outline and is the primary focus within the composition. Negative shapes are the areas around and between positive shapes, and they contribute significantly to the overall composition of an artwork.
Negative shape refers to the empty space around or between the positive shapes in an artwork. It is the area that surrounds the primary subject matter of the artwork and helps define its form and composition.