Illustrated Glossary of Organic Chemistry

Combustion (burning): A fast, exothermic chemical reaction of a fuel with an oxidizing agent (usually oxygen). Complete combustion of a hydrocarbon such as methane produces carbon dioxide and water. Incomplete combustion produces carbon monoxide.

CH4   +   2 O2

CO2   +   2 H2O
Combustion of methane.

Combustion of wood. The flames are caused by incandescence of burning gases.