A ceramic is an inorganic compound containing metals, semimetals, and nonmetals. Ceramics include a wide range of materials. The clay-based applications include bricks, tiles, clay pipe, porcelain, stoneware, and earthenware. A special category of clay is fire clay, designed to resist high temperatures. These materials are also knows as refractory materials. Glass is a ceramic used for windowpanes, lenses, bottles, light bulbs, and fibers. Cement used in concrete for construction and roadways is also a ceramic. Most abrasives and grinding wheels are made of ceramics. Many metal cutting tools are ceramic, such as tungsten carbide. Advanced ceramics generally refer to ceramic materials that have been synthetically created. Three categories of advanced ceramics are oxides, carbides, and nitrides. One major advantage of many ceramics is their ability to resist corrosion.