A frying pan, or skillet, is a broad, shallow pan with sloped or flared sides, used for searing, sautéing, and pan-frying over direct heat. The shallow, sloped shape lets liquid evaporate quickly and food be turned or tossed easily, which is what distinguishes it from a saucepan's deeper, straight sides built for holding liquid. Common materials are cast iron, carbon steel, stainless steel, nonstick-coated aluminum, and ceramic-coated pans; cast iron and carbon steel build up a seasoned patina over time and brown food well, while nonstick coatings trade some browning ability for easy release and cleaning. The wok, a deep, round-bottomed pan central to Chinese stir-frying, serves a similar searing function but is shaped to concentrate heat at its base and allow rapid tossing at very high heat.