The elements and principles of sculpture form the basis for interpreting a sculptural artwork. Artists and art historians over the centuries have developed a specific set of terms through which it's possible to discuss a sculpture's form -- that is, its construction, its effect and its style. These formal elements can be theoretically applied to any 3-D work.
Space and Mass
Sculptures by definition take up space, and it's often the way in which a sculpture affects the space between itself and its surrounding environment, or between itself and its viewer, that characterises the sculpture. Sculptors often play with negative space: empty spaces that acquire a presence because the sculpture outlines or frames them. Henry Moore famously used negative space in his Double Oval from 1966.
Scale -- the size of the sculpture in relation to something else -- is an important element in sculpture. Many sculptures are monumental, like Michael Heizer's City or Michelangelo's David, which is 17 feet high; both tower over viewers. Other sculptures might be small and intimate, like the Paleolithic Women of Willendorf statuette, which you can hold in one hand. Other sculptors use the human body to create a particular relationship with their audiences. A famous example is Martin Puryear's Self: polished, painted reddish-black and bare of ornament, the sculpture's human scale encourages its viewers to see the otherwise plain mound as a representation of a person.
Material and Texture
The material and texture of a sculpture have a profound influence on the viewer. Some materials are tactile, almost begging to be touched, like marble, while others appear coarse or slimy. The Baroque sculptor Bernini used marble to considerable effect in his famous The Rape of Proserpina. Here, the man's violent grasp on Proserpina's thigh indents the flesh, but because the sculpture is marble, Bernini's ability to craft an illusion of live flesh is a great part of the work's power.
Motion has long been an important element of sculpture. Ancient Greek statues like Myron's Discobolus captured a single moment in a discus thrower's flowing series of actions; here the moment that the sculptor chose to depict implies continued movement. Later sculptors have made sculptures that actually move. Alexander Calder's 20th century mobiles hang from the ceiling and gyrate slowly in the air -- an attempt to explore time on Calder's part.