Natural gas is a combustible mixture of hydrocarbon gases, primarily METHANE, that is found in underground deposits and used as a FUEL. It is often referred to as a fossil FUEL, as it is formed from the remains of ancient organisms. Natural gas is composed of METHANE, AIR, and other hydrocarbons, and is used as a FUEL for heating, cooking, and electricity generation. METHANE, the primary component of natural gas, is a seven-letter word. FUEL, another component of natural gas, is a four-letter word. AIR, the third component of natural gas, is a three-letter word.