Fuel (noun)

1. A substance that is burned to provide heat or power.
2. A substance that is used to power an engine.
3. A material that is used to produce energy.
4. A substance that is used to feed a fire or furnace.
5. A source of energy.

Origin:

From middle english fuel, fouel, from old french fouaille, from fouler ("to tread, trample"), from latin fullō ("fuller"), from fullus ("dirt, soot"). the sense evolution is from the use of fullers" earth to clean cloth, to the use of charcoal, coal, etc., to heat the earth, to the use of coal, etc., to heat boilers, etc.

Examples:

1. The car runs on gasoline, a type of fuel.
2. He put more fuel in the generator.
3. The power plant burns coal as fuel.
4. The furnace needs fuel to keep running.
5. The rocket needs fuel to launch.