Space

Real space is three-dimensional. Space in a work of art refers to a feeling of depth or three dimensions. It can also refer to the artist's use of the area within the picture plane. The area around the primary objects in a work of art is known as negative space, while the space occupied by the primary objects is known as positive space.

Examples: 

Positive and Negative Space
The relationship of positive to negative space can greatly affect the impact of a work of art. In this image, the woman and her kayak occupy the positive space, while the blue space surrounding her is the negative space. The disproportionate amount of negative space accentuates the figure's isolation. 

Three-Dimensional Space
The perfect illusion of three-dimensional space in a two-dimensional image is achieved through diagonal lines diminishing to a point.