A ceramic is a Rigid Material that consists of an infinite three-dimensional network of sintered crystalline grains comprising metals bonded to carbon, nitrogen, or oxygen. (IUPAC)
Note: The term ceramic generally applies to any class of inorganic, non-metallic product subjected to high temperature during manufacture or use. Or more generally to an inorganic, non-metallic, solid material comprising metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds. Almost always, the term is used to refer to artificially processes Materials. Otherwise, one often calls it a Mineral