Sculpture is the branch of the fine arts that operates in three dimensions. It is one of the plastic arts. Durable sculptural processes originally used carving (the removal of material) and modeling (the addition of material, as clay), in stone, metal, ceramics, wood and other materials but, since modernism, shifts in sculptural process led to an almost complete freedom of materials and process. A wide variety of materials may be worked by removal such as carving, assembled by welding or modeling, or molded or cast.
A basic distinction is between sculpture in the round, free-standing sculpture, such as statues, not attached (except possibly at the base) to any other surface, and the various types of relief, which are at least partly attached to a background surface. Relief is often classified by the degree it projects from the wall into low or bas-relief, high-relief, and sometimes an intermediate mid-relief.
Another basic distinction is between subtractive carving techniques, which remove material from an existing block or lump, for example of stone or wood, and modeling techniques which shape or build up the work from the material. Techniques such as casting, stamping and molding use an intermediate matrix containing the design to produce the work; many of these allow the production of several copies.
Modern and contemporary art have added a number of non-traditional forms of sculpture, including sound sculpture, light sculpture, environmental sculpture, kinetic sculpture (involving aspects of physical motion), land art and site-specific art.