Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can produce light in the form of either glowing or a flame. This process supplies most of the energy required by human civilization. Some accepted definitions of combustion are: 1. The process of burning. 2. Any process in which a substance reacts with oxygen to produce a significant rise in temperature and the emission of light. 3. A chemical process in which two compounds, such as sodium and chlorine, react together to produce heat and light. 4. A process in which a compound reacts slowly with oxygen to produce little heat and no light.