Geothermal energy – Heat that comes from the earth.

Glass recycling – Glass bottles and jars can be recycled endlessly. That means that unlike some other recycled products, a recycled bottle can be recycled into another glass bottle. And another, and so on forever.

Global warming – An increase in the average temperature of the earth, attributed to the burning of fossil fuels.

Global Warming Potential (GWP) - This is the impact of greenhouse gas emissions which contribute to the ‘greenhouse effect.' Elevated concentrations of greenhouse gases contribute to global warming and increased climate variability. Also referred to as Climate Change.

Gravity-Film Heat Exchanger (GFX) - A technology that uses the heat from hot water going down drains to preheat water in a hot water tank.

Graywater - Wastewater generated from domestic activities such as laundry, dishwashing, and bathing which can be recycled on-site for uses such as landscape irrigation, and constructed wetlands.

Greywater - Wastewater generated from domestic activities such as laundry, dishwashing, and bathing which can be recycled on-site for uses such as landscape irrigation, and constructed wetlands.

Green - The adjective used to describe people, behaviors, products, policies, standards, processes, places, movements or ideas that promote, protect, restore or minimize damage to the environment.

Green Design – A design, usually architectural, conforming to environmentally sound principles of building, material and energy use. A green building, for example, might make use of solar panels, skylights, and recycled building materials.

Green Jobs - Also known as a Green-Collar Job is, according to the United Nations Environment Program, "work in agricultural, manufacturing, research and development (R&D), administrative, and service activities that contribute(s) substantially to preserving or restoring environmental quality. Specifically, but not exclusively, this includes jobs that help to protect ecosystems and biodiversity; reduce energy, materials, and water consumption through high efficiency strategies; de-carbonize the economy; and minimize or altogether avoid generation of all forms of waste and pollution.

Green fatigue – Becoming tired with some of the constant messages of corporate green credentials and tales of impending global doom.

Green Tag - A green tag, or Renewable Energy Certificate (REC), represents the environmental attributes created when electricity is generated using renewable resources instead of fossil fuels such as coal, oil and natural gas. RECs can be sold separately from their associated electricity and enable customers to ‘green' the electricity they consume from their retail power supplier(s).

Green Washing - The practice of companies disingenuously spinning their products and policies as environmentally friendly, such as by presenting cost cuts as reductions in use of resources. It is a deceptive use of green PR or green marketing. The term green sheen has similarly been used to describe organizations that attempt to show that they are adopting practices beneficial to the environment.

Green wedding – Holding your wedding with the least environmental impact possible

Greenhouse Effect - Greenhouse gases trap heat inside the atmosphere, warming the Earth's surface

Green Technology Initiative – A consortium of companies pioneering green computing with the aim of helping to educate and inspire British businesses to become more energy efficient and environmentally responsible with their IT infrastructure.

Green wedding – Holding your wedding with the least environmental impact possible

Greenhouse effect – Explains global warming. It's the process that raises the temperature of air in the lower atmosphere due to heat trapped by greenhouse gases, such as carbon dioxide, chlorofluorocarbons, and ozone.

Greenhouse Gases (GHG) - Gases that contribute to the greenhouse effect. These include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), etc.

Greywater – Waste water that does not contain sewage or fecal contamination (such as from the shower) and can be reused for irrigation after filtration.

Ground-source heat pumps (GSHP) - Often mistakenly called geothermal heat pumps, should not to be confused with geothermal energy systems (see above). A GSHP circulates liquid through an underground loop, bringing warmer or cooler temperatures to a building depending on the season. Because it uses the constant temperature (45-50 degrees Fahrenheit) of the earth at 5-6 feet below ground, heating and cooling costs are reduced. A GSHP uses electricity for the pump, but the system is 300-400% efficient, and the payback period is generally 3-5 years. These can be installed anywhere