Pierre Grangeat's definition of tomography:

Tomography is imaging by sections or sectioning, through the use of any kind of penetrating wave. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in radiology, archaeology, biology, geophysics, oceanography, materials science, astrophysics and other sciences. In most cases it is based on the mathematical procedure called tomographic reconstruction. The word was derived from the Greek word tomos which means "part" or "section", representing the idea of "a section", "a slice" or "a cutting". A tomography of several sections of the body is known as a polytomography.