Alternative energy: Energy produced from renewable sources, such as sunlight or wind. It has the added benefit of not generating heat-trapping "greenhouse" gases.
Biodegradable: Capable of decomposing under natural conditions.
Biofuels: Fuels from recently living plants and animals, or metabolic byproducts such as manure from cows.
Bright green: An optimistic outlook that technological breakthroughs will save the day, making life more comfortable and energy efficient.
CFCs: Chlorofluorocarbons. Used in refrigerants, cleaners and aerosols and in the making of plastic foams, CFCs are greenhouse gases. They also cause ozone depletion in the stratosphere.
Compact fluorescent bulb: A smaller version of a fluorescent lamp that fits into a standard light bulb socket. Fluorescent bulbs create light in a more energy-efficient way. According to General Electric, a 15-watt compact fluorescent bulb produces the same amount of light as a 60-watt regular incandescent bulb.
Dark green: A pessimistic view of the future. It includes those who expect energy-deprived civilization to collapse and those who foresee a future that's more like the past, in which food is grown locally and people reach their destinations on foot or by streetcar rather than by automobiles.
Energy audit: The process of determining the energy consumption of a building or facility.
Environmental footprint: The impact of an organization in categories such as resource use and waste generation. A "carbon footprint" details how much carbon dioxide an organization adds to the atmosphere.
Ethanol: An automotive fuel derived from grass, sugar cane or corn. Burning ethanol adds carbon dioxide to the atmosphere, but it is seen as a renewable fuel, like solar power, that does not deplete natural resources.
Greenhouse effect: The warming of the Earth's atmosphere attributed to a buildup of carbon dioxide and other gases that retain heat and warm the planet's surface.
Hybrid cars: Autos with a small, fuel-efficient gas engine, combined with a battery-powered electric motor that assists the engine when accelerating, and an energy-recovery system from braking that fuels the battery.
Methanol: An alcohol that can be used as an alternative fuel or as a gasoline additive.
R-value: A measurement of the insulating performance of a material.
(© Copyright 2007, USA TODAY, a division of Gannett Co., Inc.)