Steam pours from the cooling tower at a nuclear power plant in Stedman, Missouri. (Corbis-Bettmann)

"Combustion" is a term often used synonymously with "burning." However, a distinction can be made that explains why combustion is more than just burning. To burn something is to set it on fire. To combust something is to subject the material (or fuel) to the process of rapid oxidation that leads to the consumption of both the material (or fuel) and the oxidizer (usually the oxygen in air) with the release of heat and light. (Usually the oxidizer is oxygen but there can be nonoxygen species, that under certain circumstances fit the definition of an oxidizer being a substance that can accept electrons in a chemical reaction.) Fires and burning involve combustion, but not all combustion involves fire in the form of visible, hot flames. There are flames that are invisible but release...