It is estimated that about 27 million Americans visit doctors of chiropractic each year, and millions more receive chiropractic care throughout the rest of the world. Chiropractic is the third largest primary health care field (after medicine and dentistry). Chiropractic is a branch of the healing arts which is based upon the understanding that good health depends, in part, upon a normally functioning nervous system (especially the spine, and the nerves extending from the spine to all parts of the body). "Chiropractic" comes from the Greek word Chiropraktikos, meaning "effective treatment by hand." Chiropractic stresses the idea that the cause of many disease processes begins with the body's inability to adapt to its environment. It looks to address these diseases not by the use of drugs and chemicals, but by locating and adjusting a musculoskeletal area of the body which is functioning improperly.