1. The process of burning a fuel with oxygen from the air to release energy, producing steam and carbon dioxide as byproducts: When a match is struck, energy is released by the process of combustion.

Unless things burn completely, toxic exhaust gases, such as carbon monoxide and other forms of pollution, are also produced.

2. An act of burning and a chemical reaction (oxidation) to produce heat, work, light, etc.. There are two main products of combustion, water vapor and carbon dioxide.

A technology that extracts heat energy from biomass so that it can then be used for a variety of heat and power applications.

An engine that burns fuel inside closed metal cylinders: Such engines that are internal combustion engines create their energy by burning fuel within themselves, as most cars do.

External combustion engines, such as steam engines, produce power less efficiently by burning fuel in an external chamber to heat a liquid or gas, which then moves a piston or a turbine.

Each piston in an internal combustion engine makes four "strokes"

The four-stroke cycles include explosions inside the engine's cylinders, on top of the pistons, and the blast force pushes the pistons down; then, the crankshaft swings around and pushes the pistons back up for the next stage in the cycle. The cycles for one piston are described in the following sequences:

1. The piston moves down, sucking in air through the inlet valve while a tiny squirt of gasoline is injected into the air.
2. The inlet valve at the top closes, trapping everything inside and then the piston moves up, squeezing the air and gasoline tightly together.
3. When the piston reaches the top, a carefully timed spark sets fire to the gasoline; as the gas burns explosively, forcing the piston back down.
4. Finally, the piston moves back up and pushes the burned gases out of the outlet valve which leave the car through the exhaust.